This paper describes some of the structure-property relations for Co and CoNi films containing Group VIB additions, i.e., chromium, molybdenum, and tungsten and Group VA additions, i.e., phosphorus, arsenic, antimony, and bismuth. All films were prepared by electrodeposition. The magnetic properties and metallurgical structure of the films with tungsten cover the same range of parameters as produced with the phosphorus films. The quantity of the elements required to achieve the maximum in coercive force increases substantially in the sequence P, As, Sb, and Bi; and in the sequence W, Mo, and Cr. The saturation moment and coercive force both decrease with increase of the concentration of added element required to attain the maximum coercive force. The quantity of the elements required is believed to be related to the ability of the electrolyte to produce a refinement of the grain size of the deposit, and the ability of the element added to segregate to the grain boundaries. The saturation moments of Co with W and P agree with the results expected for solid solutions except at high concentrations. The structure sensitive magnetic properties obtained with CoNiW films are qualitatively interpreted in the same way as for the CoNiP films, i.e., on the basis of a strongly interacting array of fine particles. The alloys containing Cr, Mo, or W possess improved resistance to aging at elevated temperatures and in corrosive environments.