Discussion: In November 1997 we published in the Cochrane Library a systematic review of mefloquine (Lariam - Roche). This is an antimalarial drug which is given prophylactically to travellers journeying to the tropics. Our review showed that mefloquine was effective in preventing malaria, but that on the basis of withdrawals from trials it was not well-tolerated. Users of healthcare interventions need good information about the harms of those interventions, particularly when (as here) the intervention is one which is offered to well people. In response to public concern, we have now summarised observational data on the non-serious adverse effects of mefloquine. In this presentation we demonstrate the approach we adopted, and recommend it as a model to be used in future Cochrane reviews.