Five complexes of transition metals with all-trans retinoic acid (HRA) have been prepared and characterized by elemental analysis, molar conductance, t.g. -d.t.a, i.r., and u.v.-vis. spectroscopy, and H-1-n.m.r. spectrometry. The general formula of these complexes is ML2. nH(2)O where L = RA, M = Mn-II, Co, Ni-II, Cu-II, Zn-II, and n = 3 or 4. They have been studied for their antitumour activity against human bladder cancer line EJ (EJ cells) with respect to proliferation, induce differentiation, P-21 and mutation P-53 expressions in vitro.