Abstract Pregastric esterase activity was detected in reconstituted nonfat milk sham fed from a nipple pail to two 4-yr-old rumen-fistulated steers. Lipolytic activity, determined in a medium containing 5% tri-n-butyrin, averaged 8.6±.4 lipase units. Further assays, in which activity was measured by free fatty acids released from a condensed milk substrate, averaged 166.9±9.2 μmol. These values are higher than those noted for young calves, indicating that secretion of pregastric esterase may persist in cattle beyond calfhood. Esterase activity in one of the steers fed whole milk until he was 2 yr of age showed no marked residual effect of earlier intake of milk fat.