The effect of 24-hour bed rest or free mobility on the frequency of complaints following diagnostic lumbar puncture was studied in a randomized trial of 111 patients aged 2 to 17 years. Patients of the bed-rest group encountered significantly more head- or backaches (positional headache 15 vs 2%; all headaches 39 vs 21%; backaches 42 vs 23%). There were no differences in the frequencies of nausea or neck stiffness. Prophylactic bed rest following lumbar puncture in children and adolescents is of no benefit and may actually be disadvantageous.