A high fat meal was given to 78 volunteers. Total esterifled fatty acid, cholesterol, and lipase levels were determined in a fasting blood specimen and in specimens obtained 3 and 6 hours after the meal. Attempts were made to correlate the fat tolerance of the individual with the level of fat splitting enzymes in the various serum specimens. The influence of Pancreatic Hormone, whole pancreatic preparations, secretin, and heparin on the fat tolerance as well as on the lipase level was determined. Attempts were made to correlate the findings of fat tolerance and glucose tolerance tests done on the same individuals.