Six dogs were, under constant environmental conditions, treated for 7 weeks with clonazepam (0.5 mg/kg b.i.d. orally). Already after 1 week of treatment, slight symptoms of withdrawal could be elicited by intravenous injection of flumazepil (Ro 15-1788). When clonazepam was finally withdrawn, a self-limiting abstinence syndrome was observed in all dogs, consisting of behavioral alterations (listlessness, wet dog shakes, dorsal recumbency), tremor, a severe clonic-tonic seizure in 1 case, hyperthermia, and weight loss. The syndrome was most pronounced on days 2 and 3 after withdrawal, after 1 week all signs of physical dependence had disappeared.