We thank the participants for their time; Pfizer, Roche, GlaxoSmithKline, and Zeneca for providing the drugs; Roche and GlaxoSmithKline for research grants; D Stürchler, J Handschin, M-L Mittelholzer (all formerly at Roche) for input in planning the study; G Miller, M Endrich (GlaxoSmithKline), M Philippi (Pfizer), and J P Fabre (Zeneca) for logistical support; P Culbert (GlaxoSmithKline, Canada), J-P Fabre (Zeneca, France), and C Taureau (Pfizer) for continuous monitoring of the quality and stability of the study drugs; Donna Merullo for assistance in the analysis of the profile of mood states data; Carmen Schwartz for translating the questionnaires from German to Hebrew; Roman Lässker for creating the ALLMALPRO (all-malaria-prophylaxis) web sites; Hans Peter Jauss for doing the figures; Maja Rentsch for data entry management of the quality of life and adverse events questionnaires; Nicola Funk for data entry of the profile of moods states; all involved in recruitment (Zürich: J Jücksel, F P Lücking, L Amsler, M Funk, M P Stürchler, and A Baños; Munich: M Santos; Basel: C H Hatz, U Legendre; Tel Hashomer: G Regev-Yochay; Frankfurt: S Franck); the medical residents at the Zürich satellite medical center on the Kenyan coast; and Albie deFrey, J Ferreira, and R Ferreira in Kruger Park for providing a back-up network of doctors in South Africa.