Ultrastructural analyses of the normal rat lens revealed a number of characteristics present regionally within the anterior and posterior polar regions: elaborate folding of the plasma membrane, including numerous microvillar processes; wide intercellular spaces at basolatteral cell borders; concentrations of mitochondria and ouabain-sensitive Na-K-ATPase activity. These features, confined primarily to the suture systems and the anterior epithelium, suggest a cortical and an epithelial involvement in ion-linked fluid transport. Acid phosphatase localized in aggregations of smooth endoplasmic reticulum at the lens fiber ends suggest this micro-organelle is a source of acid hydrolases in the normal lens.