The first experiment examined the effects of four food-deprivation schedules and four water-deprivation schedules on body weight, food intake and water intake of adult rats over ten days of deprivation and two days of recovery. During food deprivation, water intake was gradually reduced. During water deprivation, daily food intake was initially depressed but eventually returned to ad libitum levels. Consumption of restricted commodities increased over the deprivation phase. Experiment 2 showed that mutual deprivation of food and water are more apparent in rats not previously adapted to the test environment and the final experiment indicated that this was due to the inexperience of cage-naive rats in feeding under novel conditions. The results are evaluated in relation to the environmental factors that may play as great a role as physiological processes in regulating the feeding/drinking behaviour of laboratory rats.