In the course of studies by one of us (H.R.C.) on bacteriophages carried by a number of species of pathogenic Corynebacteria isolated from lesions in man and animals, evidence has been sought of similarities and differences between the properties of these phages. Although no generally acceptable method of classification of bacteriophages has yet been established, it would seem that morphology is of considerable significance in at least some types of phage (e.g. coliphages).