The phosphatase activities in the proximal tubule cells of the rat kidney were examined with light and electron microscopes. The brush border shows a strong reaction product using ATP and β-glycerophosphate, while the infolding plasma membrane shows little sign of the activity. The tubular invaginations and vacuoles also show the reaction product incubating ATP or alkaline phosphatase medium. Large granules identified as lysosomes which appear to coalesce with the vacuole possess acid phosphatase activity. No cytochemical relationship between Golgi complex and lysosomes is observed.