Saccade metrics and velocity characteristics of anticipatory as well as visually elicited saccades in horizontal and vertical directions have been measured in a group of 7 patients with Parkinson's disease (PD), a group of 6 patients with parkinsonism (PS) and a control group of 10 subjects. Twelve out of the 13 patients showed a hypometry in all directions. Four PD patients and 3 PS patients had a significantly reduced saccade peak velocity in the upward direction. Two of the 3 PS patients showed a significant reduction of peak velocity in other directions as well. Computer simulations with the Scudder model have been carried out to explain these oculomotor abnormalities. According to this model, a broadening of the collicular discharge profile initially would lead to a reduced peak velocity and with a further broadening to hypometria. On the contrary, the experimental findings in patients showed that the most important deficit is hypometria in all four directions whereas reduced peak velocity, if it is present, is not so prominent and is seen only in a limited number of directions. Therefore, it is concluded that in PD and PS the Scudder model may provide a reasonable explanation only for reduced peak velocity of upward saccades but not so for saccade hypometria.