A systematic study of the doping of the manganese site with chromium in the charge ordered Mn(IV)-rich perovskites Ca 1- xSm xMnO 3 (0.15⩽ x⩽0.5) has been performed. Whatever x, the charge ordering disappears for various chromium levels (2-13% Cr). By Cr doping, a ferromagnetic semimetallic component is induced at the expense of the antiferromagnetic state, at low temperature. An important feature deals with the expansion of colossal magnetoresistance (CMR) in all the diagram Ca 1- xSm xMnO 3 in the range 0.15⩽ x⩽0.50. This spectacular ability of chromium to induce CMR and ferromagnetism has been extended to other lanthanides, i.e. Eu, Gd and Ho, showing the influence of the A-site average size. Moreover, this study demonstrates that the charge ordering is the most stable for manganese valency close to 3.70.