Skin samples taken from foetuses of 15-19 weeks gestational age and keratinocytes were cultured by the 3T3 feeder method or in serum-free MCDB 153 medium on 16 mm coverslips. Keratinocytes taken from paediatric circumcisions and patients undergoing plastic surgery were also cultured using the 3T3 feeder method. A panel of monoclonal antibodies against a number of cytokeratins and differentiation markers were used in the PAP technique to analyse the cells. Cryostat sections taken from the donor skin samples were stained simultaneously. Foetal skin expressed the cytokeratins 7, 13 and 19 that were not observed postnatally. This cytokeratin expression as maintained in both culture conditions and also observe in paediatric and adult keratinocytes. Cytokeratin 7 was expressed on a greater proportion of foetal cells than in vivo, whereas the expression of 13 and 19 decreased. All keratinocytes expressed vimentin, transferrin receptor and Ki67 (proliferating cell antigen), while a small proportion expressed involucrin throughout culture, indicating their high level of differentiation and proliferation. No differences were observed between low and high density cultures. Foetal keratinocytes cultured in MCDB 153 did not reach confluence and stronger staining of differentiation markers was observed in these cells. These results show that the in vivo differences in cytokeratin expression of foetal and adult keratinocytes disappear in the culture.