We investigated the regulation of intercellular adhesion molecule 1 (ICAM-1) expression by the inflammatory cytokines interleukin 1 beta (IL-1), IL-6 and IL-8 in rat mesangial cells by enzyme-linked immunosorbent assay, flow cytometry and Northern blot analyses. ICAM-1 expression on mesangial cells was stimulated significantly by IL-1 beta, but not by IL-6 nor IL-8, in a dose-dependent manner. Levels of ICAM-1 mRNA were very low in unstimulated mesangial cells, while its expression was markedly induced by exposure to IL-1 beta for 3 h. IL-6 and IL-8 showed no effect on ICAM-1 mRNA accumulation. These results demonstrate that IL-1 beta, but not IL-6 nor IL-8, induces ICAM-1 mRNA and protein accumulation in rat mesangial cells.