A comparative analysis of the exocrine pancreatic secretion response with three different kinds of impure secretin was performed. Two series, carried out in Buenos Aires (Vitrum and Boots secretin), were compared with the Dreiling series (Lilly secretin) done in New York. All tests were performed with a single I.V. submaximal (1 U./kg.) dose of the hormone and with the same Dreiling technic. The evaluation showed: 1. The absence of significant differences in men among the three series. 2. Contrary to the results with the Lilly product, with both the Boots and Vitrum secretin the hydrelatic but not the ecbolic values are significantly greater in men than in women. This seems to reflect a sex-linked different sensitivity to secretin of the "pancreon" units. 3. Either in men or women the pancreatic secretion is not influenced by the age of the individual. 4. The Boots secretin results are not modified by the previous sorbitol intraduodenal infusion.