A three-way crossover study was conducted in 24 normal, male volunteers to compare the bioavailability of etintidine from capsules (2 X 200 mg) taken under fasting conditions, with food and with milk. Blood samples were collected prior to and at various times after each treatment and plasma levels of etintidine were determined by high performance liquid chromatography. Statistical analysis of the plasma etintidine concentration data indicated that while neither food nor milk had an apparent effect (p greater than 0.05) on the rate of etintidine absorption, both food alone and milk alone slightly decreased the extent of etintidine absorption. Mean bioavailability parameters of etintidine obtained following the administration of etintidine with food, milk or under fasting conditions are 5.28, 5.26 and 5.88 micrograms.h/ml, respectively (for AUC) and 1.75, 2.18 and 2.59 micrograms/ml, respectively (for Cmax), and 1.23, 1.01 and 0.91 h, respectively (for tmax). Symmetrical 95% confidence interval analyses showed that the observed decreases of less than 11% in the AUC values of etintidine following the concomitant administration of food or milk were within 17% of the fasting value and, therefore, may not be of clinical significance.