In a previous study it was demonstrated that sodium valproate, a drug that increases GABA cerebral concentrations, decreases grooming in the open field. This effect was not modified by morphine or naloxone. To provide evidence for the participation of the GABA system in the expression of grooming, other GABAergic drugs were acutely administered to rats before the test in the open field. The drugs, in the doses tested, did not modify locomotion, rearing, freezing or defaecation. Aminooxiacetic acid 10 mg/kg, barbital 60 mg/kg, baclofen 1.5 mg/kg, clonazepam 0.1 mg/kg, sodium valproate 150 mg/kg and 4,5,6,7-tetrahydroxi-azolo-5,4c-pyridine-3-ol (THIP) 0.75 mg/kg were the lowest doses to decrease the frequencies of grooming. The estimated ED50 to suppress grooming behaviour in the open field were 1.75 mg/kg baclofen, 52 mg/kg barbital, 0.86 mg/kg clonazepam and 1.0 mg/kg THIP. The decrease in grooming produced by the lowest effective doses of aminooxiacetic acid, clonazepam, sodium valproate and THIP was antagonized by concomitant administration of picrotoxin 1 mg/kg or bicuculline 1 mg/kg. The effects of baclofen and barbital on grooming were not modified by the antagonists. It is concluded that the GABA system, through GABA A and GABA B receptors may play a role in the expression of novelty-induced grooming behaviour.