This study was conducted to investigate the validity of an Activity Monitor (AM) recording functional activities in individuals with Parkinson disease (PD). A series of tasks were performed in both a fixed and a random manner by 11 participants with PD (H & Y 2-3; age range 40-79 years). Participants, wearing an AM, were recorded for video analysis (VA). The strength of association (rs) between the AM and VA for duration of time in body positions, walking, and bicycling across both fixed and random modules ranged from 0.63 to 0.98, however, the AM reported significantly greater time spent in body positions in both modules. Kappa statistics (K) between the AM and VA were the highest for transitions in the fixed module with Ks ranging from 0.74 to 1.0. During the random module, the agreement between the AM and VA was lowest for transitions between sitting and standing. In general, the Ks were low for activities lasting less than 5 seconds. The data collected in the study support the conclusion that the AM accurately evaluated the duration of time spent in body positions, the number of transitions between body positions, and the duration of time spent walking for activities lasting longer than 5 seconds in individuals with PD.