INTRODUCTION: Involuntary, localised leg cramps are common and typically affect the calf muscles at night. METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatments for idiopathic leg cramps? What are the effects of treatments for leg cramps in pregnancy? We searched: Medline, Embase, The Cochrane Library, and other important databases up to September 2008 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). RESULTS: We found 12 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. CONCLUSIONS: In this systematic review we present information relating to the effectiveness and safety of the following interventions: analgesics, anti-epileptic drugs, calcium salts, compression hosiery, magnesium salts, multivitamin and mineral supplements, quinine alone or with theophylline, sodium chloride, and stretching exercises.