Cultured human lymphocytes were treated with two typical (Levomepromazine/LVP and Perphenazine/PRZ) and two atypical (Amisulpride/AMD and Sulpiride/ SPD) antipsychotics at concentrations equivalent to the oral doses used in clinical praxis. Sister Chromatid Exchanges (SCE) were evaluated as indicators of genotoxicity and Proliferation Rate Index (PRI) and Mitotic Index (MI) were measured as indicators of cytostatic effect. Typical and atypical antipsychotics were identified as significantly (p<0.01) elevating SCE frequencies and significantly depressing PRI (p<0.01) and MI (p<0.01). A significant correlation (p<0.01) was also observed between the magnitude of the SCE response and the PRI depression achieved by the typical and the atypical antipsychotics tested. The hypothesis of a possible antineoplastic potential of these compounds is discussed.