A single dose pharmacokinetic study of a combined antimalarial formulation of mefloquine, sulphadoxine and pyrimethamine (Fansimef) has been performed in 10 healthy adult male Malaysian volunteers. The dose consisted of two tablets containing 250 mg mefloquine base, 500 mg sulphadoxine base and 25 mg pyrimethamine base each. Plasma concentrations of mefloquine and pyrimethamine were measured by GC-ECD, those of sulphadoxine by h.p.l.c. Time to peak concentrations (mean +/- s.d. for mefloquine (5.70 +/- 0.95 h), sulphadoxine (3.75 +/- 2.03 h) and pyrimethamine (3.30 +/- 1.98 h) were similar to those observed by others after administration of the single compounds. This was also true for elimination half-lives (t1/2). The t1/2s for mefloquine, sulphadoxine and pyrimethamine were 387 +/- 98 h, 255 +/- 61 h and 114 +/- 42 h, respectively.