You could spend $90 on an aluminum stepladder, but should you? What matters most is safety. You want a ladder that's strong, stable and rigid.

Consumer Reports engineers found only one that was unsafe when they tested 26 stepladders (15 wood and 11 aluminum).

Wood ladders have a number of advantages. They're usually more rigid. They don't conduct electricity. And they're generally cheaper: The average retail price for the wood ladders was $44 versus $49 for the aluminum.

Wood ladders, however, don't weather as well as aluminum. And they're heavier: Most of the wood ladders tested weighed 6 to 8 pounds more than the aluminum.

Ladders are identified according to the loads they can handle: Type I has a duty rating of 250 pounds; Type II, 225 pounds; and Type III, 200 pounds. Don't conclude that one maker's Type III is any less strong than another's Type II, however. Sometimes identical ladders carry different duty ratings. When they tested Type II and III ladders, CR's engineers found both satisfactory for household use. There was considerable overlap between the two types in performance and strength.

Nearly all the tested ladders claim to conform to Underwriters Laboratories or American National Standards Institute specifications. To carry either of those seals, for example, a ladder must be able to carry four times its duty rating.

Such labels are not an absolute guarantee that the ladder meets the prescribed standards. Also, UL and ANSI specify minimum standards of performance, and ladders that meet them can vary a lot in quality.

When you're shopping for a step-ladder, examine the step construction. On a wood ladder, if the steps are inserted in deep enough grooves and if they're held tight enough by a metal stringer (running lengthwise under the step and through the rails), they will be safe to stand on and the ladder will be fairly rigid, although CR's engineers think you still should tighten these stringers before using a new wood ladder.

In tests for strength, rigidity and stability, including tests to see how much a ladder swayed or walked, wood ladders generally had the edge over aluminum: they were more rigid, stronger, more stable -- and cheaper.

Among the best of the wood ladders in the tests were two good buys: the Rich 380 Ajax for $31, and the Sears Cat. No. 40116 for $29 plus shipping. The two top-rated aluminum ladders are relatively inexpensive: the Whitemetal Heartsavers for $49, and the Sears Cat. No. 42386 for $44 plus shipping. The thirdrated Howard 550-6 was clearly overpriced at $90.