The cDNAs for two mucins, MUC2 and MUC3, have been derived from intestinal cells, however, the mechanisms that control expression of these genes are unknown. Steady-state mRNA levels for mucin gene products were examined in HT29 colonic carcinoma cells. Cells were grown in a conventional glucose medium and a glucose-free galactose medium to induce phenotypic differentiation. Northern blot analyses using cDNA probes of MUC2 and MUC3 were performed. MUC2 mRNA levels were decreased in cells grown in galactose medium compared to glucose medium whereas MUC3 mRNA levels were increased when cells were grown in galactose medium compared to those grown in galactose-free, glucose medium. This report shows steady state mucin gene expression is altered in HT29 cells grown in a medium that induces phenotypic differentiation and may provide a model for evaluation of induction of mucin gene expression.