Two experiments were conducted to demonstrate the capacity of citrinin to cause dose-related increases in water consumption and urine excretion. In Experiment 1, chicks 24 days old were fed mixtures of untreated and inoculated corn containing citrinin to provide 0, 50, 100, 150, 200, and 250 micrograms of the toxin per gram of blended corn. The corn was fed for 4 hr, and water intake and urine excretion were measured. Chicks consumed 0, 1.23, 2.37, 3.68, 4.26 and 5.44 mg citrinin from the respective treatments. Compared with chicks consuming no citrinin, water intake and urine excretion of treated chicks increased (P less than .05) when chicks consumed 3.68 mg or more citrinin. Measures of the difference between water intake and urine excretion were similar for all treatments except for chicks consuming 3.68 mg citrinin; for those chicks the difference was significantly greater (P less than .05) than for chicks consuming 1.23 mg citrinin. In Experiment 2, inoculated corn was heated in a microwave oven for 1, 2, 8, and 16 min. Temperatures of the heated corn samples, when removed from the oven, were 76 C, 100 C and 105 C, respectively. Chicks that were 28 days old were fed these various samples of corn for 4 hr. Heating corn for 2 min to a temperature of 76 C caused no apparent loss of citrinin activity based on water intake and urine excretion measures. Heating the corn for 8 min to a temperature of 100 C destroyed some of the citrinin activity. Heating citrinin-contaminated corn to 105 C for 16 min destroyed the diuretic effect of the mycotoxin.