In a two-factorial experiment, 420 1-day-old male commercial broiler chickens were randomly divided and fed a basal diet with or without vitamin C (500 parts/10(6)). Half of the birds within each group receiving the same kind of feed were fed a T-3 supplemented diet from day 1, in order to increase the ascites incidence. Weekly body weight and feed intake were measured. Venous blood samples were taken from 10 birds per group weekly from day 14 on, for haematocrit measurements, blood gas analysis, measurement of thyroid hormones and lactate/pyruvate ratios. Ascites mortality was recorded daily.