A single 40 mg/kg dose of praziquantel (PZQ) continues to be the standard treatment for schistosomiasis caused by S. mansoni and S. haematobium in all clinical settings. Experimental development of drug resistance and the recent isolation of S. mansoni strains with a natural tolerance to high doses of PZQ have raised concerns over the adequacy of such a dose. We describe two Spanish travelers with genitourinary schistosomiasis caused by S. haematobium in whom repeated standard treatment failed to clear the infection.