Our objective was to study the efficacy of transcutaneous electrical nerve stimulation (TENS) in reducing pain during the first stage of labour. Using a prospective randomized placebo-controlled, double blind clinical trial, a patient-controlled analgesia system was used to measure differences in outcome. Trials took place in a labour unit at the St. Antonius Hospital, Nieuwegein, The Netherlands, during a period of 18 months. Forty-six patients, during the first stage of labour, were treated with TENS, and 48 with a placebo apparatus. Main outcome measures were pain relief, amount of administered analgesics, obstetrical and neonatal outcome, and side effects. No significant differences occurred between groups in the number of requests for pethidine/promethazine. The foetal outcome in both groups was the same. TENS and placebo were considered equally effective by both patients and staff. In conclusion, TENS was not more effective than a placebo apparatus in relieving pain during the first stage of labour. No adverse side-effects occurred.