Hereditary pancreatitis (HP) is an autosomal dominant disease. Two heterozygous missense mutations, R122H (R117H) and N29I (N21I), in the cationic trypsinogen gene have been clearly associated with HP. The 'self-destruct' model proposed for the R122H mutation is discussed in connection with the existing theory of pancreatitis, and the basic biochemistry and physiology of trypsinogen, with particular reference to R122 as the primary autolysis site of the cationic trypsinogen. Two different genetic mechanisms are identified which cause the R122H mutation, and gene conversion is the likely cause of the N29I mutation. A unifying model, which highlights an indirect impairment on the R122 autolysis site is hypothesised for the N29I mutation. Possible predisposition to pancreatitis by additional DNA variants in the gene, such as the A16V signal peptide cleavage site mutation and the K23R activation peptide cleavage site mutation is suspected, but not proven. Evidence of genetic heterogeneity of HP is reviewed and cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations detected in HP families are re-evaluated. Finally, large scale association studies are expected to clarify the additional variants' role in pancreatitis and to identify new HP genes.