The distribution of non‐specific carboxylic esterases (Ec 3.1.1) in the digestive tract of perch,Perca fluviatilisL., was investigated histochemically using 1‐naphthyl acetate as the substrate. Strong enzymatic activity was present in the gastric glands and surface cells of the stomach, intestinal mucosa of the pyloric caeca, upper and middle intestine, pancreas (exocrine cells) and liver. The enzymatic activity in the lower intestine and rectum was weak. The activity was not demonstrated in the oesophagus or pyloric sphincter. In the intestine, the activity was localized in the columnar cells especially in the supranuclear cytoplasm. The enzymatic activity demonstrated in the digestive tract of perch using 1 ‐naphthyl acetate represents combined esterolytic and lipoproteolytic act