A double-blind crossover design was used to evaluate the effect of two different formulations of prazepam, on motor and cognitive functions and subjective symptoms. Ten healthy male volunteers received 20 mg of prazepam both in tablet and liquid (as drops) formulation, separated by a 1 week interval. All subjects completed a battery of 9 performance tests 2.25 h and 4.75 h after drug intake (corresponding to the times of peak plasma concentration). They also rated themselves on eight visual analogue scales before, 2 h, 4.5 h and 8 h following drug intake. A significant difference between liquid drops and tablets was demonstrated in 4 of the 9 performance tests and 2 of the 8 items of the self rating scales. These results suggest that a single dose of prazepam administered in liquid drop form exhibits greater sedative properties than the same dose administered as tablets in healthy volunteers, probably as a result of more rapid absorption.