A controlled randomized double-blind study was done to determine the frequency and severity of leg cramps in 40 patients on dialysis with a history of leg cramps. All patients entered a 2 month placebo washout and were randomized into a 2 month double-dummy phase of quinine 325 mg at bedtime versus vitamin E 400 IU at bedtime. Of the 29 patients completing the study, 16 received quinine and 13 vitamin E. During placebo washout, the vitamin E group had a mean of 10.4 leg cramps per month, and the quinine group had a mean of 10.9. The vitamin E and quinine groups had a 1 month reduction in leg cramps to 3.3 and 3.6, respectively (p < 0.0005 for both groups combined); this was sustained at 2 months. A severity of pain index showed a statistically significant decrease for both groups. The 95% confidence interval for the difference between the number of leg cramps after vitamin E versus quinine treatment (95% confidence interval, -3.8, +3.2) suggests similar efficacy. Quinine and vitamin E were effective treatments for leg cramps in these patients. Considering the potential toxicity of quinine, vitamin E is recommended as the initial treatment of choice for patients on dialysis with leg cramps.