This study examines kinematic patterns of upper and lower lip movements in bilabial stop production with particular emphasis on events before and during the oral closure. Lip movements were recorded using a magnetometer system. Five subjects participated and produced 50 tokens of the sequences /aCV/, where C was either /p/ or /b/ and V one of the vowels /i, a, u/. Force of labial contact and oral air pressure were also recorded in one subject. The results indicate that at the instant of oral closure, the velocity of both lips was close to peak velocity. They also show that the lower lip continued its upward movement after oral closure. This was reflected in the force of labial contact, which showed an increase in contact pressure after the oral closure had occurred. During the period of lower lip upward movement after the oral closure, the upper lip often showed a corresponding upward movement, suggesting that the lower lip might be pushing the upper lip. These results support the hypothesis that one goal in making the lip closure is a region of negative lip aperture. [Work supported by NIH.]