Background: quinine is a common treatment for nocturnal leg cramps but has potential side effects. An uncontrolled study suggested that calf-stretching exercises could prevent nocturnal leg cramps (night cramps) but these findings have never been confirmed. Aim: to assess the effect of calf-stretching exercises and cessation of quinine treatment for patients with night cramps taking quinine. Design of study: randomised controlled trial. Setting: twenty-eight general practices in southern England. Method: one hundred and ninety-one patients prescribed quinine for night cramps were randomised to one of four groups defined by two 'advice' factors: undertake exercises and stop quinine. After 6 weeks they were advised that they could take quinine and undertake the exercises freely. Documentation of cramp at 12 weeks was achieved in 181 (95%) patients. Main outcome measures were: symptom burden score, and frequency of night cramps and quinine usage. Results: at 12 weeks there was no significant difference in number of cramps in the previous 4 weeks (exercise = 1.95, 95% confidence interval [CI] = -3.01 to 6.90; quinine cessation = 3.45, 95% CI = -1.52 to 8.41) nor symptom burden or severity of cramps. However, after 12 weeks 26.5% (95% CI = 13.3% to 39.7%) more patients who had been advised to stop quinine treatment reported taking no quinine tablets in the previous week (odds ratio [OR] = 3.32, 95% CI = 1.37 to 8.06), whereas advice to do stretching exercises had no effect (OR = 0.73, 95% CI = 0.27 to 1.98). Conclusions: calf-stretching exercises are not effective in reducing the frequency or severity of night cramps. Advising those on long-term repeat prescriptions to try stopping quinine temporarily will result in no major problems for patients, and allow a significant number to stop medication.