Somatostatin 28 is derived from the cleavage product of prosomatostatin. Somatostatin 28 is present in very small quantities, in the pancreas, S-28(1-12) LI consist mainly of S-28(1-12) and 9-11,000 mol wt S-28(1-12) LI, 9-11,000 l wt S-28(1-12) LI could represent prosomatostatin without the S-14 sequence, the finding of high concentrations of 9-11,000 mol wt S-28(1-12) LI suggests that S-14 synthesis can occur independently of S-28 and that direct processing of prosomatostatin is an important pathway for S-14 synthesis in the pancreas.