BACKGROUND Infection with head lice is a widespread condition in developed and developing countries. Infection occurs most commonly in children, but also affects adults. If left untreated the condition can become intensely irritating and skin infections may occur if the bites are scratched. OBJECTIVES The aim of this review was to assess the effects of interventions for head lice. SEARCH STRATEGY Trials register of The Cochrane Infectious Diseases Group; Medline; Embase; Science Citation Index; Biosis and Toxline; reference lists of relevant articles; pharmaceutical companies producing pediculicides (published and unpublished trials); UK and US Regulatory Authorities. SELECTION CRITERIA Randomised trials (published and unpublished) or trials using alternate allocation were sought which compared pediculicides with the same and different formulations of other pediculicides, and pediculicides with physical methods. DATA COLLECTION AND ANALYSIS Of the 70 identified studies, only three met the inclusion criteria and one is awaiting assessment. Two reviewers independently assessed trial quality. One reviewer extracted the data. MAIN RESULTS We found no evidence that any one pediculicide has greater effect than another. The two studies comparing malathion and permethrin with their respective vehicles showed a higher cure rate for the active ingredient than the vehicle. The third study comparing synergised pyrethrins with permethrin showed their effects to be equivalent. Adverse effects were reported in a number of trials and were all minor, although reporting quality varied between trials. REVIEWER'S CONCLUSIONS Permethrin, synergised pyrethrin and malathion were effective in the treatment of head lice. However, the emergence of drug resistance since these trials were conducted means there is no direct contemporary evidence of the comparative effectiveness of these products. The 'best' choice will now depend on local resistance patterns. There is currently no evidence from trials to indicate the effectiveness of physical methods, such as combing/'BugBusting' or other chemical control methods such as the use of herbal treatments, when used in the curative treatment of head lice. Future trials should take into account the methodological recommendations that arise from this review.