A prospective study of 200 patients undergoing lumbar radiculography using 10 ml iohexol (240 mgI/ml) was undertaken to determine whether the procedure could be safely performed on an out-patient basis. No statistically significant differences in the incidence and severity of side-effects were found between the 99 out-patients and 101 in-patient controls. Three out-patients had to be kept in hospital at the end of the observation period and a further three out-patients were re-admitted to hospital because of severe side-effects. Out-patient lumbar radiculography is a safe procedure provided there is careful patient selection, adequate advice and easy access to medical help should problems arise following the examination. Adopting this practice considerably reduces the cost of lumbar radiculography and indirectly increases the availability of orthopaedic beds.