Fine particles of Co have been prepared in the size range of 50 - 350 angstrom by the vapor deposition technique. The dependence of magnetization on size and temperature has been studied. A maximum coercivity of 1500 Oe was obtained for a particle size of 350 angstrom. The magnetic and structural measurements indicate a shell-type structure with a fcc Co core surrounded by a Co-oxide shell. The effect of exchange interactions between the antiferromagnetic Co-oxide shell and the ferromagnetic Co core on the magnetic behavior of the powders has been investigated.