The potential role of intercellular adhesion molecule 1 (ICAM-1) in the biology of human melanoma cells has stimulated interest in the characterization of its modulation. The present study has shown that the differentiating agent retinoic acid (RA) up-regulates ICAM-1 expression by melanoma cells in a dose- and time-dependent fashion. The enhancement of ICAM-1 cell surface expression is paralleled by an increase in ICAM-1 mRNA. Therefore, ICAM-1 represents an additional gene which may be transcriptionally regulated by RA. The five melanoma cell lines tested displayed a differential susceptibility to the modulation of ICAM-1 expression by RA, since the cell line MeWo did not change in its ICAM-1 expression following incubation with RA. Nevertheless, RA-insensitive as well as RA-sensitive melanoma cell lines displayed a higher increase in ICAM-1 expression following incubation with RA and cytokines than following incubation with each of them. Analysis of the distribution in the melanoma cell lines of retinoic acid receptors (RARs) showed a relationship between susceptibility to a RA-mediated increase of ICAM-1 expression and RAR beta expression, suggesting that the latter receptor may play a role in the phenomenon. RAR alpha and RAR gamma were present in RA-sensitive and -insensitive melanoma cell lines, suggesting that they play a role in the enhancement by RA of cytokine-mediated up-regulation of ICAM-1 expression. The melanoma cell lines we have described may represent a useful system for investigating the role of RAR in the regulation of gene expression and the mechanism(s) which underlie this effect.