Four studies treating methodological and clinical aspects of the question of driving ability of the mentally ill under psychopharmaca have been discussed. The complexity of the integral interplay in the domain of physiological, emotional, and psychomotor-cognitive functions relevant for driving behaviour makes an equally complex experimental design appear necessary to tackle this problem. Although the various test apparatus marketed for the investigation of driving fitness allow a relatively proper estimate, the examination of mentally ill patients under psychopharmaca calls for the differentiated inclusion of physiological, pharmacological, pharmacokinetic, pschomotor-cognitive, and personality-specific dimensions. The present state of science requires the repeated judgment of the treating therapist in addition. This judgment can only be made on the basis of a partnership between doctor and patient.