Exocrine pancreatic marker (immunoreactive-trypsin) and endocrine Beta-cell function (plasma insulin and C-peptide during an oral glucose tolerance test) were studied in 40 subjects with tropical-calcific-pancreatitis [seven non-diabetic, seven with impaired-glucose-tolerance and 26 diabetic (fibro-calculous-pancreatic-diabetes)]. In non-diabetic and impaired-glucose-tolerance subjects there was evidence of active pancreatitis in some and exocrine function was partially preserved. Fibro-calculous-pancreatic-diabetic subjects showed severely diminished exocrine pancreatic function; none showed 'pancreatitic' elevation of immunoreactive-trypsin. Beta-cell function was preserved in non-diabetic and impaired-glucose-tolerance subjects; diabetic subjects showed variable Beta-cell function but it was severely diminished in more than 75%. Immunoreactive-trypsin and C-peptide were directly correlated (rs = 0.55, p less than 0.01). This cross sectional study demonstrates, for the first time, that the Beta-cell loss in tropical-calcific-pancreatitis is related to the exocrine loss. It suggests that diabetes in tropical-calcific-pancreatitis is either secondary to pancreatitis or that a common factor(s) acts simultaneously on both components.