During the last seven years 14 patients with lumbar disc hernias were admitted who presented with a short period of sciatica before experiencing relief of pain accompanied by paresis. Ten patients had marked paresis and were operated on, most of them during the first week after the start of paresis. Three patients had minor paresis in regression, and one patient suffered complete paralysis for five months. These four patients were not operated on. Motor function improved significantly in nine out of ten operated patients. Four of them had no paresis at all. The three patients with mild paresis in regression still showed some motor impairment 9-24 months later, and the condition of the patient with paralysis remained unchanged. In conclusion, patients who develop painless sciatica and marked paresis deteriorate seriously, and early surgery is necessary in order to avoid permanent disturbance of motor function.