A study was performed to determine the efficacy of praziquantel (PZQ) against Schistosoma haematobium. Children (n = 592) infected with S. haematobium received either a single treatment with PZQ (40 mg/kg) or two or three treatments with PZQ at three-week intervals after the initial treatment and efficacy was monitored for nine weeks. Cure rates at three-weeks post-treatment were low (< 50%), suggesting either that worms are killed very slowly or, more likely, that eggs continue to be released from tissues after worm death. Interestingly, a single dose of PZQ showed high efficacy (cure rate > 83% and egg reduction rate > 98%) when assessed from six weeks post-treatment onward. There were no significant differences in cure rates or intensity of infection between the three cohorts at any point in the study, despite the different treatment regimens. Since children were in contact with transmission sites during the study period, the results suggest good efficacy of PZQ against all stages of S. haematobium, including the immature worms.