Pregnant women participating in a longitudinal immuno-epidemiologic survey in Lambaréné, Gabon, and presenting with Plasmodium falciparum parasitemia at monthly blood smear examinations were offered treatment with oral 7-day quinine monotherapy according to national health guidelines. A total of 50 pregnant women were offered 7-day oral quinine sulfate 10 mg/kg thrice daily. Clinical examinations and laboratory tests were performed on Days 28 and 56 to assess the effectiveness of this standard regimen. By Day 28, the effectiveness of the 7-day quinine regimen was 60% (95% confidence interval: 46-72%). We conclude that a 7-day course of quinine has a poor effectiveness and that alternative treatment regimens for malaria in pregnant women should be assessed.