The number of reduced cobalt metal surface atoms in Co/TiO2 was found to increase with the presence of rutile phase. It was suggested that the increased number of reduced cobalt metal surface atoms be attributed to highly dispersed cobalt oxide species as seen by the transmission electron microscopy (TEM) technique. Besides the dispersion of cobalt oxide species, it should be noted that the presence of rutile phase in titania could facilitate the reduction of highly dispersed cobalt oxides species into the reduced cobalt metal surface atoms. It was concluded that both highly dispersed cobalt oxide species and the presence of rutile phase could result in the large number of reduced cobalt metal surface atoms. © 2005 Elsevier B.V. All rights reserved.