The effect of pH, time and dietary source of cadmium on the ' in vitro' digestion of food and its 'in vivo' absorption by mice were investigated. The effect of pH on the adsorption and release of cadmium from fresh and dry lettuce ('Lactuca sativa' L. cv Ostinata) in the absence of gastric and intestinal enzymes and the effect of gastric pH on the absorption of cadmium from the diet was also determined. Lettuce amended with soluble Cd-salt and lettuce with Cd incorporated during growth were compared using the soluble fraction of the metal after gastric and intestinal digestion. The lettuce was digested using a protocol simulating the conditions of both gastric and intestinal digestive phases. Because the soluble fraction of the cadmium decreased during the intestinal phase, further studies were performed to understand the effect of pH on cadmium adsorption to lettuce. The soluble fraction of cadmium from a 1 ppm solution mixed with lettuce decreased when the pH increased, suggesting that cadmium binding by the food would be increased in parts of the intestine where the pH is more alkaline. It was hypothesized that gastrointestinal pH affected cadmium absorption from food and organ accumulation and this hypothesis was tested 'in vivo' by pharmacological manipulation of the gastric pH of mice exposed to cadmium amended diets. Gastric pH in our experiment did not affect cadmium absorption 'in vivo'.