Introduction: The purpose of this study was to gain additional insight on patterns of behavior of three individuals dually diagnosed with intellectual disability (ID) and bipolar disorder as they cycled between elevated and depressed mood states. Methods: Data were collected from weekly, one-hour observations across a period of several months. The total duration of time spent engaged in target responses (pacing, rocking, and talking), in addition to indirect measures of activity (Irritability and Hyperactivity subscale of the Aberrant Behavior Checklist-Community; ABC-C), were assessed to characterize and monitor changes in overall state. Results: While observable behavior seemed to be a good indicator of overall state, ABC-C Irritability and Hyperactivity subscales were not. Additional analyses included lag sequential analyses of environmental stimuli and conditions potentially correlated with observed behavior. Conclusions: Our findings suggest that observable behavior may be one way to monitor the progression of bipolar disorder in those with ID; however, further research needs to be conducted.