Treatment of mouse fibroblast BALB/c 3T6 cells with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate or the antipromoter retinoic acid affects the release of several glycoproteins into the medium. The phorbol ester decreases the secretion of a 180-kd and 160-kd glycoprotein and increases the release of a 38-kd glycoprotein. In contrast, retinoic acid affects these glycoproteins in the opposite way. Moreover, retinoic acid enhances the level of a 55-kd and 60-kd glycoprotein. The 180-kd and 160-kd glycoproteins appear sensitive to collagenase and after pepsin treatment are converted to bands which comigrate with collagen alpha 1 (I) and alpha 2 (I). These glycoproteins are tentatively identified as being pro alpha 1 (I) and pro alpha 2 (I). The 38-kd glycoprotein appears to comigrate with the major excreted protein. Retinoic acid appears to reduce significantly the incorporation of mannose into secreted glycoproteins whereas treatment with the phorbol ester induces an enhancement in mannose incorporation. Our results indicate that both phorbol esters and retinoids alter the release of several glycoproteins from 3T6 mouse fibroblasts. These changes appear to relate to the influence of these compounds on the expression of the transformed phenotype of these cells.