Compared with blood plasma, rete testis fluid (RTF) from rams was found to contain a higher concentration per unit volume of the enzymes that occur in the sperm acrosome and in the kinoplasmic droplet, but the levels of these enzymes could be reduced by high-speed centrifugation. Other enzymes present in blood plasma were also found in RTF but at a lower concentration per unit volume. Because of the low concentration of protein in RTF, however, the activity of most of these enzymes per unit weight of protein was higher in RTF than in blood plasma. The concentrations of these enzymes and the total protein concentrations were only slightly reduced by high speed centrifugation. There was no appreciable concentration of the X-isoenzyme of lactic dehydrogenase in RTF and the activity of most enzymes per unit weight of protein was less in RTF than in the testis.