The diagnostic value of the fecal chymotrypsin test (FCT) was reevaluated with regard to (a) proved pancreatic hypofunction of different severity (183 pancreozymin-secretin tests); (b) the final clinical diagnosis, and (c) fecal fat excretion (208 patients with chronic pancreatitis; CP). Progressive pancreatic disease (cancer, CP) was mainly associated with moderate or severe pancreatic hypofunction (119/138; 86.2%) and a low incidence of false-normal FCT values (14/138; 10.1%). Miscellaneous disorders (mainly reversible pancreatic hypofunction) were mainly associated with slight pancreatic hypofunction and a high incidence of false-normal FCT values (17/45; 37.8%). Pancreatic steatorrhea (greater than 10 g/day) was found only in patients with markedly depressed FCT values. Progressive deterioration of pancreatic function was demonstrated by repeated FCT in CP (n = 220).