Schistosoma mansoni infected mice were treated with a single oral dose of either praziquantel (400 mg/kg) or oxamniquine (100 mg/kg). The uncured mice, after the first dose, were given a second dose of the same drug or alternatively with the other drug. The drug efficacy was monitored by stool examination and egg count using Kato-thick smear technique. Praziquantel was found to be more effective, it gave 60% cure rate after the first dose, increased to 100% after the second dose, than oxamniquine which had 37% and 74% cure rates respectively. Furthermore, in uncured mice praziquantel resulted in more egg count reduction than oxamniquine. Treatment with the alternate drug of mice not cured with the first treatment gave 100% cure rate with praziquantel and 83% with oxamniquine. It was concluded that praziquantel is generally more effective than oxamniquine and cases not cured with a single dose of either drugs may be effectively treated with a second dose of the other.