Secondarily generalized convulsive status epilepticus was induced by intraperitoneal (i.p.) injection of D,L-homocysteine thiolactone to rats with actively epileptogenic cobalt lesions in motor cortex. This induced focal motor seizures which secondarily generalized. Control animals not treated with antiepileptic drugs had a mean of 18.3 generalized convulsions over a mean period of 103.8 min. Electrographic patterns seen during status epilepticus are described and are very similar to those seen during human status epilepticus. Phenytoin, phenobarbital, diazepam and lorazepam were all effective in arresting the generalized seizures when given i.p. after the second such seizure. Efficacy was serum drug concentration dependent. Concentrations effective in arrest of generalized seizures in this model are similar to those reported to be effective in the treatment of human status epilepticus. Diazepam ED50s for control of generalized tonic-clonic seizures and for arrest of all seizure activity were determined.