Region-specific antisera to three enkephalins: met-enkephalin, met-enkephalin-Arg6-Phe7 and met-enkephalin-Arg6-Gly7-Leu8, together with four region specific antisera to progastrin: C-terminal G17 specific, N-terminal G34 specific, cryptic peptides A- and B-specific, were used in immunohistochemical studies of hog antral mucosa. A sub-population (6-10%) of the gastrin-containing endocrine cells (G-cells) was found to react with antisera to met-enkephalin, met-enkephalin-Arg6-Phe7 and met-enkephalin-Arg6-Gly7-Leu8. About 30% of all the enkephalin-containing cells were identified as G-cells. The results indicate that a fraction of G-cells produces both enkephalin-like peptides and gastrin.