This article presents acoustic evidence for the existence of a bilabial implosive, [ƃ], in one variety of U.S. English. One articulatory observation is that vocal chord vibration of the English bilabial stop, /b/, can only be maintained for a maximum of about 82 ms. Increasing the vibration beyond this threshold is only possible by increasing the size of the vocal cavity, which in turn is often enabled by lowering the glottis, a gesture characteristic of implosive stops. The authors compare the voiced bilabial stops of five white males from the Western united States, three of whom impressionistically appear to have implosive stops and two who do not. For each stop, a normalized stop duration was calculated based on speech tempo, the actual stop duration, and the percentage of the stop that displayed vocal fold vibration. As far as normalized stop duration is concerned, there are no significant differences between the five speakers. However, the vocal fold vibration patterns for the two nonimplosive-sounding speakers and the three implosive-sounding speakers differ a great deal. In addition to evidence for biliabial implosives, there are large differences in the percentage of stop closure that displays vocal fold vibration. Both of these factors merit further study in terms of their social distribution in English, which is not known for implosion.