The ability of garlic preparations to inhibit cancer cell-growth has been attributed to a group of structurally-related organosulfur compounds found in the crushed clove. Historically, interest has centred on three such compounds as allicin, diallyl disulfide and diallyl trisulfide, with less interest on E- and Z-ajoene. A recently developed synthetic route from our laboratory for preparing ajoene analogues allows access to derivatives containing the sulfoxide / vinyl disulfide core whilst varying the terminal end-group functionality. A small library has been synthesized and an advanced lead with p-methoxybenzyl end groups (8) identified. Data on the in vitro anti-proliferation activity of compound (8) is presented here against six cancer cell-lines in comparison with that of Z- and E-ajoene to reveal an enhancement in activity of up to twelvefold. In addition, a modest selectivity is observed for tumour over normal cell-lines of up to threefold. Data on ajoene and its derivatives is presented in the context of chemosensitization in drug-resistance, and ideas on ajoene's mode of action at the molecular level are presented and discussed.