To study water imbalance reported to occur in vitamin A deficiency, chronic hypovitaminosis A was produced in 7-week old rats by feeding deficient or adequate vitamin A (12 or 256 µg/kg body weight/day, respectively) for a comparison period of 6 weeks. In the case of the deficient rats, these were partially depleted of their vitamin A stores prior to feeding the 12 µg intake. At the termination of the comparison period, the deficient rats exhibited elevated cerebrospinal fluid pressure, and lower plasma and liver vitamin A concentrations. Based upon kinetics of a single intrajugular injection of 3H2O and 14C-inulin, total body water, extracellular water and renal clearances were lower in vitamin A deficient rats. However, when these criteria were expressed on a body weight basis, there were no significant differences. The turnover of total body water was reduced in the hypovitaminotic A rats. The results are discussed in terms of an inhibitory effect of vitamin A deficiency on growth.