A 2 year old girl presented with fever, malaise, a maculopapular rash and lymphadenopathy followed by the onset of haemolytic anaemia and massive splenomegaly. Serology was consistent with acquired toxoplasmosis. A 6 week course of pyrimethamine resulted in a rise in the haemoglobin and reduction of the splenomegaly. During the subsequent 10 years, pyrimethamine treatment of three similar acute episodes resulted in similar clinical responses. There was no spontaneous improvement in the haemolytic anaemia or splenomegaly when pyrimethamine was initially withheld for 6, 1, and 1.5 months respectively during three of these episodes. Investigations did not reveal an immunodeficiency state. This case suggests the possibility of a previously unreported causal association between acquired toxoplasmosis and haemolytic anaemia in a child.