Systemic toxic reactions to local anesthetics are brought about by absolute overdosage, and, most commonly, inadvertent intravascular injections. The anticonvulsant action of ketamine has been studied. However, the effect of ketamine on lidocame-induced convulsions has not been reported. This study investigated the effect of ketamine on lidocaine-induced seizures in mice. Mice (3241 g) were divided into 2 groups, 15 in each group, and were pretreated with intraperitoneal normal saline solution or intraperitenoeal (ip) ketamine before lidocaine. Group I (N = 15) received 75 mg kg ip lidocaine; Group 2 (N = 15) received 20 mg kg ketamin ip; 5 min later 75 mg kg lidokaine ip were applied. Clinical features, incidences, latencies, durations, and mortality rate of convulsions were recorded. After 75 mg kg lidocame injection, ataxia, loss of righting reflex, and generalized tonic-clonic convulsions were seen within 2-5 min in Group 1. Generalized tonic-clonic convulsions were seen in 8 mice and deep sedation was seen in 7 mice in Group 2 (p <.05). Generalized status epilepticus occurred in one mouse in both groups. Three mice from Group I and one mouse from Group 2 died during convulsions. There were no differences between the two groups with regard to the onset and duration of seizures (P >.05). It was concluded that ketamine significantly prevented lidocaine-induced generalized tonic-clonic seizures; on the other hand, the lethality of lidocame was least reduced by ketamine.