A 16 year old schoolgirl with an established peripheral neuropath (motor conduction velocity in peroneal nerve of 5 metres/sec., absent sural nerve potential and CSF protein of 160 mg%) presented with a progressive worsening to the point of physical incapacitation over the course of 23 days. Serum phytanic acid was 33 mg/100 ml. Following the exhibition of prednisolone she was discharged walking well after 5 days. After 3 weeks the steroid medication was stopped and a phytanic acid free diet instituted. Despite continued abnormal electrophysiological findings, (e.g. motor conduction velocity in peroneal nerve 3 metres/sec., and in ulnar nerve 8 metres/sec), she remains well three years later. It is probable that the steroid medication had a pronounced beneficial effect, though the mechanism of action remains unexplained.