This study examines the question of how native Yoruba speakers distinguish word-initial [gb] and [b]. It describes an experiment in which two factors are examined: prevoicing and CV formant transitions. Minimal pairs were recorded, and in one set of data, prevoicings were switched, and in another, the steep portion of the CV formant transition from the [gb] was removed and spliced into the [b] recordings. Yoruba subjects identified virtually 100% of the unmodified recordings correctly, but only 75% with switched prevoicings, and 56% with the CV excised and respliced. Results thus show that both of these are used as cues in distinguishing Yoruba [gb] and [b].