Densities of metal films were measured using multiple beam interferometry in combination with an oscillating crystal microbalance. Film densities of Al, Au, Ag, Cr, and Cu were found to be independent of thickness within experimental accuracy of about 5% in the thickness range from 200 to 5000 Å for fixed deposition conditions. Measurements indicate that film densities were equal to bulk densities within measurement accuracy for Al, Au, Ag, and Cu for deposition at about 10−6Torr. The film density of Cr was found to be strongly dependent on oxygen partial pressure above 10−6Torr, decreasing sharply as the oxygen partial pressure increased. The effect of condensation coefficients of metal films on the optical measurements is discussed.