Two distinct analytic methods have been used to identify the function of problem behavior. The antecedent-behavior-consequence (ABC) method (Iwata, Dorsey, Slifer, Bauman, & Richman, 1982/1994) includes the delivery of consequences for problem behavior. The AB method (Carr & Durand, 1985) does not include consequence delivery, instead relying exclusively on antecedent conditions to evoke the behavior. The AB and ABC functional analysis methods were compared in this study with 4 children with developmental disabilities who engaged in task-related problem behavior. Results show that the ABC method identified an escape method for all four cases, whereas the AB method failed to identify a function for any case. (Contains 1 figure and 1 footnote.)