The study was carried out in 12 children aged 6 months to 2 years, with uncomplicated falciparum malaria admitted to the Hospital for Tropical Diseases, Bangkok. They were treated with mefloquine in the form of MSP (mefloquine 250 mg+sulfadoxine 500 mg+pyrimethamine 25 mg) at a single dose of 25 mg mefloquine base/kg body weight. All of them were cured (28 days follow-up) with minimal side effects. Pharmacokinetic parameter determination was carried out in 9 cases. The results revealed that MRT, t1/2 and tmax in this study (children 6-24 months old) are comparable to the values in children aged 5-12 years, but shorter than in adult patients. Cmax and AUC in children 6-24 months old are comparable to those in children of 5-12 years, but much higher than in adult patients. Vz/f values in this study are comparable to those in children 5-12 years old, but lower than in adult patients.