The effect of growth retardation, resulting from feed restriction for a prolonged period, on the course of infection with Trypanosoma vivax was studied. Twelve male castrated West Africa Dwarf goats were subjected to a restricted feeding reghen of 55 g pelleted lucerne (Medicago safiva)/kg body weight^0·75 per d for on average 17 weeks. Twelve other animals were fed on pelleted lucerne ad libitum, resulting in a normal growth pattern. After this period, all animals were fed on pelleted lucerne ad libitum, and six animatn of each previous feeding regimen treatment were infected with Trypanosoma viva. The other animals served as controls. In week 2 and 4 post infection (pi) energy and N balaoces were measured. In the week before infection and daring infection blood biochemical and clinlcal variables were measured. At 2 weeks before, and 4 weeks after infection, a liver biopsy was taken for measurement of triacylglycerol. Iofection caused intermittent fever and anaemia. The first peak of fever persisted longer in iofected anlmaln with normal growth than in infected animals with retarded growth. Gross energy and metabolizable energy intake, and energy retention were reduced ininfected animals. Metabolizable energy requirements for mainteoaoce were increased by infection. Plasma non-esterified fatty acids (NEFA) and glucose concentratioos were increased in infected animals, whereas serum triiodothyronine and thyroxine coocentratioos were decreased.Plasma urea concentration and liver triacylglycerol were uoaffected. No interaction of growth retardation with infection with respect to blood biochemical variables was found, apart from plasma NEFA in week 2 pi. N retention was not significantly affected by treatments. In conclusion, minor indications were found for an interaction between growth retardation, as applied in the present study, and trypaommiasis infection in West Africao Dwarf goats with respect to energy and N metabolism.