A functional analysis (FA) is the most commonly used assessment methodology for identifying maintaining variables influencing problem behavior. However, if an FA does not produce clear differentiation, researchers and practitioners often then modify procedures to include additional individualized variables. The interview-informed synthesized contingency analysis (IISCA) provides a marked departure from FA methodology and aims to include individualized factors at the initiation of the assessment in order to more rapidly produce differentiation and clear results. We sought to further evaluate and compare the outcomes of two different functional analysis methods: the single-contingency functional analysis (FA) and the interview-informed synthesized contingency analysis (IISCA) to determine the function of problem behavior and evaluate the subsequent function-based treatment determined from the functional analysis results with two children diagnosed with autism spectrum disorder (ASD). Both participants engaged in problem behavior maintained by single-contingencies of reinforcement identified within the single-contingency FA and emphasized by the effectiveness of each single-contingency function-based treatment.