452 previously healthy children aged over six months and under six years were admitted to the Sheffield Children's Hospital between January, 1972, and December, 1976, after their first convulsion associated with fever. 304 of the children had a lumbar puncture. 25 punctures were necessary according to defined clinical criteria--including those in 15 children who were subsequently shown to have meningitis. All 148 children who did not have a lumbar puncture made a prompt and uneventful recovery. Children with convulsions associated with fever should be referred to hospital. A lumbar puncture should be performed when meningitis is suspected, after examination by a senior and experienced member of the staff. It should not be carried out as a routine procedure.