The binding of dexamethasone-receptor complexes to RNA was investigated by an assay system under cell-free conditions. By this gradient centrifugation assay, we found that, under low salt concentrations, dexamethasone-receptor complexes can bind to 18S RNA from HeLa cells. Molybdate, tungstate and methavanadate were able to inhibit dexamethasone-receptor complex binding to 18S RNA, whereas this was not the case when chloride, fluoride, or sulfate ions were present in our binding assays. Molybdate was also found to disrupt dexamethasone-receptor-18S RNA complexes once they were already formed. We concluded that interaction between dexamethasone-receptor complexes and RNA under cell-free conditions is affected by ions present in the medium.