Electroplating of cobalt onto steel substrates from citrate baths has been investigated under different conditions of bath composition, current density, pH and temperature. A detailed study has been made of the influence of these variables on the potentiodynamic cathodic polarization curves, cathodic current efficiency and the throwing power as well as the throwing index of these baths. The optimum bath composition has been established and it contains: CoSO4. 7H(2)O (0.36 mol dm(-3)) trisodium citrate (0.19 mol dm(-3)) and citric acid (0.1 mol dm(-3)) at pH 5.0. The microhardness of cobalt electrodeposited from citrate baths is high and it may be, under certain conditions, two or three times higher than that reported for cobalt electrodeposited from other different baths. The surface morphology of the as-plated cobalt was investigated by using scanning electron microscopy (SEM) while the structure was studied by using X-ray diffraction analysis and anodic stripping voltammetry (ASV) techniques.