To evaluate the effectiveness of exocrine function tests in diagnosing chronic pancreatitis (CP), we compared the sensitivity and specificity of duodenal intubation with tubeless tests. While the secretin test (ST) was necessary to diagnose CP, especially in noncalcified CP, and tubeless tests demonstrated insufficient sensitivity to diagnose CP, the combination assay of tubeless tests was specific enough to diagnose severe exocrine dysfunction. Our studies found the sensitivity of secretin testing to diagnose definite CP to be 87%. In patients with probable CP, 60% had mild exocrine insufficiency and 40% had normal function. The false-positive rate of the ST results in nonpancreatic diseases, except diabetes mellitus, was 5%. The correlation between morphological changes in endoscopic retrograde pancreatography (ERP) and exocrine function evaluated by ST was 74%. In patients with calcified CP, 81% had parallel results between ERP and the ST, but in noncalcified CP, 47% had parallel results. In patients with severe or moderate exocrine insufficiency demonstrated by ST, abnormally low levels were observed in 63% by N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) test, 61% by fecal chymotrypsin test (FCT), and 44% by pancreatic amylase (PA). In patients with normal exocrine function demonstrated by ST, abnormally low levels were observed in 28% by BT-PABA test, 28% by FCT, and 10% by PA. A combination assay of BT-PABA test, FCT, and PA improved the specificity for diagnosing CP but not the sensitivity.