In three trials, single or multiple doses of citrinin dissolved in 0.5 N-NaOH and adjusted to neutral pH with HCl were given to rabbits by either the oral or intraperitoneal route. The 72-hr LD50 was 50 mg/kg body weight by intraperitoneal administration and 134 mg/kg by the oral route. The primary clinical sign in rabbits receiving a single oral dose of 125-150 mg citrinin/kg was fluid diarrhoea commencing 8 hr after dosing. Pathological alterations were generally confined to the kidney and consisted of degeneration and necrosis of proximal convoluted tubules and straight segments. In rabbits given a single oral dose of citrinin (130 mg/kg) the earliest histopathological change, seen 8 hr after dosing, was cytoplasmic vacuolation of tubular epithelial cells. Rabbits given a single oral dose of 120 mg citrinin/kg had regeneration of renal tubular epithelium accompanied by slight tubular cell necrosis when examined 7 days after dosing. Rabbits given multiple sublethal doses of citrinin (33.5 or 77 mg/kg daily for 7 days) had renal alterations of mild tubular degeneration and necrosis, and tubular regeneration.