The pancreolauryl test is marketed as a tubeless test of pancreatic function based on the specific splitting by pancreatic esterase of orally administered fluorescein dilaurate. We have evaluated the test in 50 patients, all of whom had at least one other pancreatic function test (secretin-pancreozymin, Lundh, BT PABA/14C index). The sensitivity of the pancreolauryl test was 75% if equivocal results (T/K 20–30) were excluded and 77% if the equivocal results were included amongst the abnormal results – figures which were similar to those obtained for the other three function tests. However, the specificity of the pancreolauryl test was 60% if equivocal results were excluded, decreasing to only 39% if equivocal results were considered to be abnormal. The false-positive tests chiefly occurred in patients who had previously undergone gastric or biliary by-pass, or vagotomy and cholecystectomy (BT PABA/14C test normal). These data, and the known dependence of esterase activity on bile salts, suggest that the pancreolauryl test assesses the combined functional efficacy of secreted esterase and bile salts. Despite the test’s high sensitivity, its low specificity makes it unreliable as a test of pancreatic function per se. The pancreolauryl test may be particularly useful in evaluating patients with bile-pancreatic juice admixture problems.