The authors systematically treated 94 patients with West syndrome using the same protocol of sodium valproate and steroids, starting with hydrocortisone (HC) orally for two weeks. If seizures stopped, HC was withdrawn; if they persisted, tetracosactrin (TA; synthetic ACTH) was administered for another two weeks then HC was slowly withdrawn. 90 per cent of the symptomatic cases were controlled by HC, the remainder by TA. 65 per cent of symptomatic cases were controlled by HC; this rose to 78 per cent if patients treated by HC then TA were included. At 31 months follow-up, the percentage of favourable results was 72 per cent for cryptogenic and 60 per cent for symptomatic cases. For the latter, best results were obtained in patients with periventricular leukomalacia, postnatal distress and porencephaly. Patients suffering from sequelae of full-term distress or encephalopathy of unknown aetiology were the most resistant.