Balb/3T3 fibroblasts were cultured in type I collagen gel and the effects of tretinoin (all-trans-retinoic acid) were examined on cell growth and the gel contraction produced by cells. Cell proliferation was suppressed and the degree of gel contraction was enhanced by the addition of 10(-7) and 10(-6) M tretinoin. Growth and gel contractility of transformed cells derived from the Balb/3T3 cells were not influenced by this agent. Addition of 12-O-tetradecanoylphorbol ester, which is known to antagonize tretinoin in several biological processes, enhanced gel contraction synergistically with tretinoin. These results suggest that tretinoin influences cell-to-collagen interactions.