Comparative tests were performed on male albino rats to study the activity of the original hydroxylamine barbiturate HB-7, with phenobarbital (PhB) and pentobarbital (PB) using the conflict situation test (after Vogel et al., 1971) with thirsty rats (deprived of water for 48 hours). The three barbiturates studied (HB-7, PhB and PB) were administered intraperitoneally in four doses (5, 10, 15 and 20 mg/kg). Two parameters were registered: number of punished responses (electrical shocks punishing attempts to drink) and the number of non-punished responses (approaching the drinking tube) for the 5-min period of observation. In a second group of experiments the same test was used to study the effect of picrotoxin and of its combinations with the effective doses of HB-7, PhB and PB. The three barbiturates tested were found to have an anxiolytic effect, i.e. to increase the number of attempts to drink water, in the higher doses used. Picrotoxin causes a decrease in the number of punished responses (anxiomimetic effect). When HB-7, PhB and PB are combined with picrotoxin, the latter eliminates their anxiolytic action. The conclusion reached is that the anxiolytic action of the barbiturates tested is probably connected with an effect on the GABA-ergic transmitter system in the central nervous system.