A series of Calpha,alpha-disubstituted cyclic derivatives of N-(phosphonomethyl) glycine have been synthesized and characterized. They exhibited moderate clastogenicity, low antiproliferative activity on mice bone marrow cells and well expressed cytotoxicity against human tumor cell lines. The 8- and 12-membered cyclic analogs proved superior to the remaining compounds and were found to trigger apoptotic cell death in DOHH-2 cells. The latter compound caused 50% inhibition of the viability of hemobastose-derived cell lines at concentrations ranging from 20 to 67 microM.