A study has been conducted of the two major cues for stop consonants: the burst of the stop release and the transition of the formants in the adjacent vowels. Detailed frequency vs intensity spectra of the bursts were prepared, while the transitions were studied by means of Sonagraph records. Possible criteria for identification were developed and tested. In order to assess the efficacy of the two major types of cue, perceptual tests were conducted with isolated segments containing either stop bursts or vowel transitions alone. [This work was supported in part by the Signal Corps, the Office of Scientific Research (Air Research and Development Command), and the Office of Naval Research.]