This study has clinical implications. Stuttering and cluttering are defined by the authors as communication disorders characterized by disturbances of rhythm and rate of speech. The two aspects are often confused. Stuttering involves blockings, repetition, and prolongations in rhythm. Cluttering is characterized by a rapid rate of speech accompanied by repetitions, additions, inversions, omissions, and distortions of sounds, syllables, words, or phrases. Using tape recorded segments of reading which were analyzed for various rate and rhythm factors, the authors conclude that automated analysis of 'on-off' speech patterns provides some basis for a diagnostic differentiation between stuttering and cluttering.