In recent years considerable attention has been given to evaluating the relationships between actinomycete development and the earthy taste and odor problems frequently encountered in potable waters. Increased concern over these problems has resulted in extensive inquiries concerning the isolation and enumeration of those actinomycete groups which may significantly affect water quality. In an effort to help fill this need, procedures are set forth in considerable detail so that they can be adopted by investigators who have had little experience with this group of organisms. The methods described are well established techniques that have been employed with considerable success.