Jejunal lactase and sucrase activities were demonstrated in biopsy specimens obtained endoscopically using a rapid test which had been developed previously. The results were compared with enzyme activities determined by Dahlquist's method. The data suggest that the rapid test is suitable for the demonstration about the presence of lactase and sucrase, and the results are correlated with enzyme activities measured by assay. The main advantage of the test, that it is rapid, simple and cheap, no special equipments are necessary, so it can be used in every endoscopic department.