110 patients with proven chronic pancreatitis have been studied to assess the prevalence of the various Pi phenotypes of alpha1-antitrypsin in this disease compared with a control group of 116 blood-donors. The phenotype PiMZ (including Mweak) was significantly more prevalent and PiMM significantly less so in the patients with pancreatitis. It is possible that a heterozygous deficiency of this protease inhibitor renders the pancreas more vulnerable to aetiological agents (e.g., alcohol).