We studied 10 subjects each with melancholic depression evidencing significant motor retardation (RM), Parkinson's disease (PD) with bradykinesia, and normal healthy controls (NC), matched closely for age and gender, on measurements of motor function and depression, and their performance of simple and complex ballistic movements. The simple movements involved the execution of 10 degrees, 20 degrees, and 40 degrees angular movements using a methodology adapted from Hallett and Khoshbin (1980). The complex movements involved the performance by the right arm and hand of a squeeze and a flexion movement, both sequentially and simultaneously, using a methodology adopted from Benecke et al (1986, 1987). The RM and PD groups demonstrated a smaller increase in the angular velocity as the angle of the movement increased from 10 degrees to 40 degrees than did the NC group. Many PD and RM subjects showed multiple electromyographic (EMG) bursts during the ballistic movements. The RM and PD subjects tended take longer to perform the simultaneous and sequential movements, but nonsignificantly so. The RM group performed the squeeze movement slower when executed as part of the simultaneous movement than when performed as a simple movement. The pause time between the movements when performed sequentially was longer (nonsignificantly) for the RM subjects. Our study demonstrated a disturbance in the execution of simple and complex movements by RM subjects that resembled the disturbance seen in PD. This argues for a common pathophysiological basis for at least some aspects of motor retardation in the two disorders. Reduced dopamine function is one common abnormality that may partially account for these findings.