Corticosterone has been shown to affect several patterns of glial cell and neuronal development. We have previously reported that exogenously administered corticosterone preferentially accumulated into the retinas of 8-day-old chick embryos. Moreover, we observed that it affects muscarinic cholinergic binding. Thus, we investigated the effect of different concentrations of corticosterone on retinal cells in culture. Retinas were dissected from 8-day-old embryos, dissociated and cells plated on salt-precipitated collagen. At day 5, cultures were treated with corticosterone (from 10(-9) M to 10(-7) M) for 24 h. Controls received either Dulbecco's Modified Eagle Medium (DMEM) plus 10% fetal calf serum (FCS) or DMEM only. Results show that the main effect of the hormone was inhibition of neuronal process outgrowth. Also cell aggregation, flat cell proliferation and confluency are altered in hormone-treated cultures. All these effects are reversible and can be attributed to hormone effect and not to serum deprivation.