TGF$aL, a member of the epidermal growth factor family stimulates proliferation of various cells. In the search for molecules that regulate cell division in the lens epithelium, the effect of numerous growth factors including EGF and FGF has been determined. In this study, the effect of TGF$aL on lens epithelial cells (LEC) from rabbit and monkey was investigated and compared to FGF and EGF. Since TGF$aL is suggested to be a factor that is regulated by auto and/or paracrine mechanisms, an immunohistochemical visualisation of the factor in the rabbit lensin situwas performed.TGF$aL stimulates LEC in a dose-dependent manner with a maximal threefold increase in cellular proliferation at 100 ng/ml. At a concentration above 10 ng/ml the cells lost their epithelial morphology and became irregular and star-shaped. Since TGF$aL is a potent LEC mitogen and has shown to increase in aqueous humour after trauma to the eye, this factor might be one of the molecules that regulate normal cell division in the ocular lens as well as LEC growth after cataract surgery.