Abstract The purpose of this study was to develop a systematic functional assessment package for aberrant behaviors maintained by nonsocial (automatic) reinforcement. The assessment package included four components: (1) functional analysis, (2) antecedent assessment of specific automatic reinforcement sources, (3) stimulus preference assessment, and (4) treatment evaluation. Functional analysis data indicated automatic reinforcement functions of the stereotypy exhibited by a 10-year-old male and the self-injury (SIB) exhibited by a 30-year-old male. Antecedent assessments of sensory classes indicated that auditory stimulation and tactile stimulation were associated with stereotypy and SIB, respectively. A multiple-stimulus-without-replacement procedure was conducted with each participant to identify the most- and least-preferred stimuli within the identified sensory classes. In an attempt to validate the assessment package for each participant, a DRO procedure was implemented using a reversal design with a multielement component. DRO procedures using stimuli within the targeted sensory classes were successful in eliminating the aberrant behaviors of both participants. The results are discussed in the context of improving the methodology for assessing and treating automatically reinforced behaviors.