The effects of Dexamethasone (Dex) on Glycosaminoglycan (GAG) accumulation were examined in the murine fibroblast line C3H/10T1/2. Confluent cultures were treated with the hormone and then labelled with either [3H]acetate or [3H]glucosamine and analyzed for [3H]GAG content. Dex could inhibit the accumulation of [3H]GAG in a dose dependent manner with a half maximal response achieved at approximately 5nM and a maximal response at approximately 100nM. Higher concentrations failed to influence precursor incorporation further. The response was seen after 6 hours of hormone exposure and was nearly maximal by 10 hours. The incorporation of [3H]leucine into protein was unaffected by Dex treatment. 11 alpha hydrocortisone, an inactive steroid, failed to elicit a cellular response. Thus it appears that glucocorticoids regulate GAG accumulation in a rodent fibroblast line as they do in primary human skin fibroblast cultures.