Male guinea pigs received sodium ascorbate solution [equivalent to 1 g ascorbic acid/(kg body weight.d)] by intraperitoneal injection for 4 wk. During the ascorbic acid treatment period, plasma and urinary ascorbic acid levels rose markedly. Three weeks after the ascorbic acid treatment was withdrawn, mean urinary ascorbic acid levels were significantly lower than their corresponding basal levels. At both 2 and 5 wk after withdrawal of ascorbic acid treatment, mean plasma ascorbic acid levels were below normal. The results indicate that these animals had experienced a transient withdrawal effect after administration of large doses of ascorbic acid that lasted about 1 wk. This, in turn, indicates that the rate of ascorbic acid turnover was probably increased during treatment, and this effect persisted even after the ascorbic acid was withdrawn. Examination of data from each individual experimental animal revealed that the pattern of urinary ascorbic acid excretion after the withdrawal of large doses of ascorbic acid varied from animal to animal. Among the twelve experimental guinea pigs, seven had abnormally low urinary ascorbic acid levels 2-4 wk after the withdrawal of the large doses of ascorbic acid.