Dendritic cobalt nanocrystals have been synthesized by the reduction of Co2+ with hydrazine hydrate in ethanol via a room temperature solution synthetic route. The magnetic coercivity H-c of as-prepared cobalt dendrites came up to 500 Oe at room temperature. We chose different solvents to control the phases and morphologies of the cobalt products. (C) 2003 Elsevier B.V. All rights reserved.