We identified quantitative studies on how often traditional plant based treatments for malaria were used, and results from all these studies were combined (as a meta-analysis) to give an overall average frequency of use. We added up the number of patients reporting the use of herbal medicines, and then we divided by the total number of patients surveyed in all the studies. We reviewed qualitative sociological and anthropological studies and extracted and summarised key themes.

We searched ethnobotanical studies from malaria endemic countries for plant species reported for the treatment of "malaria" or "fever". These we entered into a database and assigned an "IVmal" (importance value for the treatment of malaria) according to how widely its use was reported. Conservation information for each species came from the 2002 IUCN Red Data book online (www.redlist.org).

Clinical studies were categorised according to the study design (case reports, cohort studies, controlled trials) and to species of malaria. Each study was scrutinised for measures of efficacy (most commonly parasite clearance and clearance of fever or symptoms) and safety (reports of side effects or changes in haematological, biochemical, or electrocardiographical variables).