BACKGROUND The aetiology of transient lumbar pain (TLP) after spinal anaesthesia has generated much interest. Many theories have been discussed. Early ambulation has been suggested as one plausible theory for developing TLP. METHODS A total of 107 patients scheduled for inguinal hernial repair under spinal anaesthesia (20 mg/ml hyperbaric lidocaine) were randomised to either early or late ambulation: the early ambulation (group A), as early as possible after total regression of spinal block or the late mobilisation (group B) bedridden for more than 12 h. The clinical course and duration of operation were monitored. Assessments 4, 8 and 12 h after spinal anaesthesia were performed with respect to wound pain, nausea, tiredness and eventual symptoms of TLP were recorded. The patients also kept a diary about any symptoms once daily day 1-3 at home. A telephone follow-up was performed at day 5-7. RESULTS Our results showed an incidence of TLP of 23% in all patients. No difference was recorded between early and late mobilisation patients, 12 and 13 patients, respectively. CONCLUSIONS Early ambulation does not seem to increase the risk of developing TLP.