Quantitative analysis of gait was performed in 20 parkinsonians before and 1 h after the acute administration of L-Dopa in order to discriminate between the Dopa-sensitive and the Dopa-resistant kinematic gait parameters. The stride length and the kinematic parameters (swing velocity, peak velocity) related to the energy were Dopa-sensitive. The improvement of the bent forward posture by L-Dopa may explain the stride length increase. Temporal parameters (stride and swing duration, stride duration variability), related to rhythm, were Dopa-resistant. Experimental data argue for the importance of force control in maintaining the posture. The stride length variability, possibly related to the variability of force production shown to exist in parkinsonians was not significantly improved by L-Dopa. In Parkinson's disease different hypotheses might explain the inexorable aggravation of gait disorders along the course of the disease: (1) an advancing disorder of coordination between postural control and locomotion, (2) if some gait parameters like stride length and kinematic parameters are Dopa-sensitive, the others are Dopa-resistant and thus may involve other mechanisms than dopamine deficiency.