The hypothesis that a gastrin-like peptide is acting as an autocrine growth factor in gastric and colonic carcinoma cell lines requires that the cells should synthesize a gastrin-like mRNA. Although no gastrin mRNA was observed in the gastric line Okajima or the colonic lines HCT 116 or LIM 1215 by Northern blotting, gastrin mRNA was detected by application of the polymerase chain reaction. Two products were observed corresponding to mRNA with and without a 130 bp intron. The sequences of both products were identical to the sequences predicted from the normal human gastrin gene.