Judging from the prevalence of antibodies to Toxoplasma gondii in the serum, toxoplasmosis is a highly prevalent infection in the United States.1 However, surprisingly little is known concerning the extent and types of clinically definable illness this parasite causes.2 Several factors have contributed to this lack of knowledge, the major one being the difficulty in establishing the diagnosis. The small number of laboratories where reliable serological tests and proper interpretation of results are available for the diagnosis of toxoplasmosis contributes to this difficulty.
An ideal study to define the nature of toxoplasmosis in a human population should be prospective and should involve attempts to isolate and identify the parasite from suspected and accessible sources and the collec tion and testing of sera for Toxoplasma antibodies at frequent intervals, particularly during the acute and convalescent stage of each manifest illness. Data thus obtained should make it possible to determine