The long-term effect of lithium treatment on the digestive and absorptive function has been investigated in male albino rats. The uptake of D-glucose, amino acids and activities of cellular and brush border enzymes were evaluated after every 3 months. Significantly increased uptake was observed in 6-month lithium-treated rats. The absorptive capacity (Vmax) for D-glucose increased significantly without alteration in the Michaelis constant. Activities of cellular, brush border membrane disaccharidase, leucine aminopeptidase and Na+,K+-ATPase enzymes were significantly augmented in 6-month lithium-treated animals. The elevation in sucrase activity may be due to induction of enzyme since only Vmax was increased in lithium-treated animals. The present biochemical alterations suggest that long-term lithium ingestion stimulates the small bowel digestive and absorptive functions.