Dietary surveys are important for understanding food consumption patterns in national studies, clinical research, and patient counseling. Portion size estimation aids usually increase accuracy of consumers' reports of the amount of food they ate in dietary surveys. However, wedge-shaped foods (eg, pie, cake, and pizza) pose special problems; this shape is not easily estimated by previously available portion size estimation aids. In focus groups, respondents indicate they need a portion size estimation aid that is easier to use than a ruler for portion estimation of wedge-shaped foods. An adjustable wedge was developed and tested with 320 respondents, ages 18 to 65 years, of various races and education levels, and both sexes, in four states using multiple sizes and types of wedge-shaped foods. The accuracy of portion size estimation with the two portion size estimation aids was assessed. The adjustable wedge gave similar results to the ruler for most portions tested, but was more accurate (P<0.05) than the ruler in approximately one third of comparisons. Both aids resulted in substantial misestimation, indicating that regardless of aid some people have difficulty estimating portions of wedge-shaped foods. The adjustable wedge was easy for people to use and can be recommended as an option for estimating portion size of wedge-shaped foods.