Sodium lawsonate (SL: derivative of lawsone, hydroxy-1,4-naphthaquinone) was studied for its activity profile in mice and rats, with emphasis on actions on the central nervous system. The drug produced a cataleptic state, hypothermia and loss of active avoidance behaviour, but it did not augment barbiturate sleep. The catalepsy was prevented by hyoscine (mice) or by sodium salicylate (rats). SL did not affect apomorphine-sterotypy (a dopamine-mediated behaviour) but blocked the lithium-induced head twitches (a serotonin-mediated behavioural response). SL did not produce excitation, analgesia or exhibit anti-MES activity. All actions of SL were rapid in onset and brief in duration. In view of effective dose range (40-80 mg/kg, i.p.) and MLD 50 values (76 mg/kg, i.p., in mice; 122 mg/kg, i.p., in rats), safety index of SL appears to be low.