W arehouse clubs such as BJ's Wholesale Club, Sam's Club and Costco Wholesale can really save you a lot of money. In the past, they sold mainly bulk food and household goods in a no-frills environment. Recently, they have started offering everything from eyeglasses to insurance.

Be careful, though. Many items purchased at warehouse clubs cost more than those purchased at traditional stores. Here, the best and worst deals...

Big savings

Your savings on these great club buys will more than cover the annual cost of membership -- $45 at BJ's, $50 at Costco, $40 at Sam's...

Eyeglasses. Many warehouse club locations now have on-site optical departments that turn out well-made eyeglasses for about 50% less than your local optician -- a savings of $60 or more per pair. Some locations offer eye exams -- contact lenses may be available as well. Prices are comparable to those at discount Web sites, but you don't pay for shipping.

Small, disposable nonfood items. These products are perfect as bulk purchases because they don't go bad or take up much storage space. Expect to save up to 50% off of supermarket prices -- sometimes more. Among the best buys: Toothbrushes, razor blades, dental floss, soap, deodorant, garbage bags, sandwich bags, printer toner cartridges, contact lens supplies and batteries.

Example: A name-brand toothbrush might cost $3 in a supermarket. In a discount club, you'll pay perhaps $5 for a six-pack of the same brush, an annual savings of $13 per family member if you change brushes every two months, as recommended by most dentists.

Caution: Batteries and contact lens supplies eventually go bad, so avoid buying more than you can use before their expiration dates. Don't store extra toothpaste and deodorant in the bathroom -- they'll last longer if kept in a cool, dry place.

Alcoholic beverages. Wine, beer and liquor at warehouse clubs sell for 20% to 25% below supermarket and liquor store prices. However, you might have to buy bigger bottles. You'll find top brands as well as warehouse club brands.

Note: The sale of alcohol by warehouse clubs is prohibited in some states. Generally speaking, if supermarkets in your state are allowed to sell alcohol, then warehouse clubs can as well.

Gasoline. Many warehouse clubs now have their own on-site gas stations -- with prices that typically are 10 to 20 cents per gallon lower than other stations in the region. If you drive 10,000 miles a year in a vehicle that gets 25 miles to the gallon, that 10- to 20-cent discount translates into $40 to $80 a year -- as long as you don't have to go too far out of your way to get to the warehouse club.

Prepaid phone cards. Warehouse clubs sell domestic long-distance phone cards for as little as three cents a minute. That's a better rate than you're likely to find on prepaid calling anywhere else.

Caution: No matter where you purchase them, prepaid phone cards are a good deal only if you actually use them. Roughly 20% of all minutes purchased on prepaid phone cards are never used because the cards are lost or forgotten.

shop with caution

Savings are possible at warehouse clubs on the following items, but shop carefully -- you might find better prices elsewhere...

Consumer electronics. Warehouse club prices on consumer electronics likely are below the regular prices at other major retailers. Warehouse clubs, however, may not stock a good selection of leading brand names... and special offers are common on consumer electronics elsewhere. You might find an even better deal during a sale at a national chain or on-line at such sites as Overstock.com and Buy.com.

Canned and frozen foods. Even in a can, food doesn't stay fresh forever. Buying canned foods in bulk makes sense -- but only if you'll consume it within a year. Bulk purchases of frozen foods are smart if you have the freezer space -- for example, if you have a second freezer in the basement.

Insurance. Some warehouse clubs now offer auto and homeowner's insurance -- but their prices may or may not beat quotes you can get elsewhere, so don't buy until you have shopped around. To compare insurance rates, check out www.insure.com or www.insweb.com.

Diet beverages. These drinks start to lose their sweetness after three or four months. Don't buy in bulk unless you'll drink it all before then.

Caution: If your warehouse club (or any store) keeps carbonated beverages outside in the summer, don't purchase these bottles or cans. Prolonged exposure to heat can rob soda of both sweetness and flavor. Similarly, don't store soda in a hot garage.

Bad deals

Not everything for sale at a warehouse club is a money saver...

Bulk perishable foods. Warehouse club prices for perishable foods typically are no better than supermarket prices. Supermarket profit margins on food are so thin that it's tough for clubs to do much better -- and if food bought in bulk goes uneaten, you lose money.

Examples: Spices aren't a wise bulk purchase -- they start to lose their flavor in as little as two months, and many attract insects. The five-liter tins of olive oil that are sold at warehouse clubs are a good deal only if you can get through that much olive oil in a year. After that, it will begin to go rancid.

Premier memberships. Some warehouse clubs try to sell special high-end memberships. For an extra charge each year, you can get additional savings and exclusive offers. These premier memberships don't make sense unless you're buying in quantity for a restaurant, business or large family.

Smart shopping strategies

Other ways to make warehouse shopping more advantageous...

Avoid the dolly. Warehouse clubs offer customers large dollies to wheel through the aisles. The size of these dollies makes even large purchases look small -- until you get to the register. Stick to a shopping cart to keep purchases in perspective.

Use coupons selectively. Some warehouse clubs accept coupons, but because so many food items are packaged in unusual sizes and quantities -- and since warehouse clubs offer limited brands -- you're better off using coupons at the supermarket for items that you buy regularly. Besides, unlike many supermarkets, warehouse clubs don't have double or triple coupon days.