We used a computational analysis of open loop handwriting movements and a clinical rating scale for monitoring the effect of apomorphine in 16 patients with early untreated parkinsonism [subsequently L-DOPA responsive, probable Parkinson's disease (PD)], six patients with long-standing PD with L-DOPA associated motor fluctuations, and seven patients with known L-DOPA unresponsive parkinsonism. Subjects were instructed to write fluently concentric circles of ∼ 12 mm in diameter. Movements were recorded for two periods of 3 a each, using a digitizing tablet. Mean Peak velocity (Vmax) and mean peak acceleration (Amax) were determined. In addition, two sensitive indices describing the degree of automation of handwriting were derived: (a) NCV, calculated as the mean Number of Changes in direction of Velocity per half circle, and (b) NCA, the mean Number of Changes in the direction of Acceleration. Clinical rating was performed according to the Unified Parkinson's disease Rating Scale part III (UPDRS III). After apomorphine injection, the patients with early untreated probable PD showed significant improvement of Vmax'Amax' NCV, NCA, and UPDRS III scores. Likewise, the patients with long-standing PD improved significantly in all kinematic parameters and UPDRS III scores. Patients with L-DOPA unresponsive parkinsonism failed to change significantly in any of the parameters tested. These observations suggest that the computer-assisted analysis of automated handwriting movements can be used as an objective quick method for quantifying dopamimetic effects on the kinematics of handwriting movements in parkinsonian patients.