Intrarectally (i.r.) administered diazepam (DZP) solution at doses of 20 and 30 mg in the treatment of serial seizures was studied in 39 adult patients with refractory partial epilepsy. Patients were randomly distributed into two groups (20 mg, n = 21; 30 mg, n = 18). Plasma levels of DZP were assessed over 24 h following i.r. injection. The efficacy of i.r. DZP in the treatment of serial seizures in adults was confirmed; onset of effect was noted approximately 10 min after the injection, and the effective dose was 0.50 mg/kg. Tolerance and acceptability were good. Intrarectal injection of DZP can be performed even by unskilled personnel and may be recommended in patients with serial seizures in the hope of preventing development of status epilepticus.