Several clinical and experimental findings suggest that abnormal serotonin (5-HT) function may be involved in movement disorders such as dystonia, and it was proposed that selective 5-HT1A receptor antagonists may be of benefit in treating such disorders. In the present study, the novel, highly selective and silent 5-HT1A receptor antagonist (+)-WAY-100135 (N-tert-butyl-3(4-(2-methoxyphenyl)piperazin-1-yl)-2-phenylprop ionamide) was tested in an inbred line of Syrian hamsters with generalized dystonia, i.e. a frequent movement disorder in humans. In order to demonstrate that WAY-100135 acts as a 5-HT1A receptor antagonist in the hamster, the drug was shown to antagonize the behavioural syndrome induced by 8-hydroxy-2-(di-n-propylamino)tetralin. When administered at 5-HT1A receptor antagonistic doses in dystonic hamsters, (+)-WAY-100135 dramatically aggravated the dystonic attacks. The data thus suggest that, in contrast to previous theoretical proposals, 5-HT1A receptor antagonists provide no novel therapeutic approach to involuntary movement disorders such as dystonia.