The mean 24 hr. urinary amylase excretion for 192 human subjects on a self selected mixed diet was 3095 units [plus or minus] 1024. The following changes in amylase excretion were observed after 4 days of fasting or 4 days on the following diets: High carbohydrate and alkaline residue diets caused a significant decrease in urinary amylase excretion; fasting and high protein diets resulted in a significant increase in amylase excretion; no change was observed on ketogenic and high purine diets. The wide differences in urinary amylase excretion caused by dietary inbalances indicate this enzyme may have some function in the body other than that performed in digestion.