This proposal is a request for partial support for the Fifth International Toxoplasmosis Conference. This meeting will take place at the Marconi Conference Center in Marshall, California, May 1-6, 1999. This meeting is important as it fosters research concerning Toxoplamsa gondii and Toxoplasmosis. Toxoplasmosis causes loss of sight, hearing, cognitive function and life in congenitally infected and immuno- compromised patients. Research findings from work with Toxoplasma gondii often also are applicable to other Apicomplexan infections, such as malaria which kills 2-3 million children each year and Eimeria infections which cause substantial agricultural losses. The scientists who attended the earlier 4 conferences have found them very important for their work, and the meetings have resulted in significant advances in this field. The growing literature on the subjects covered in the last conference reflects not only the efforts of the individual scientists, but also productive collaborations that have resulted from the meetings. The group of session chairs, all of whom have accepted and are eager to participate (see attached), consists of many leaders, and up-and-coming leaders in the field. Almost all of the best scientists working on toxoplasmosis from around the world will attend this special meeting. The meeting also will include younger scientists, women and minorities. Meeting participants will discuss recent, and as yet unpublished, research findings. Such findings often form the basis for new diagnostic tests and treatments. Subject discussions will range from molecular biology, cell biology, immunology and biochemistry of the parasite to epidemiology, pathogenesis, diagnosis, prevention, and treatment of the clinical diseases. A brief general summary of concepts discussed (but not including as yet unpublished data), will be submitted to Parasitology Today in order to make resources from the meeting available to advance work for all in the field.