In addition to cycle-by-cycle (jitter) and long-term (intonation contour and declination) changes, vocal fundamental frequency (Fo) is known to vary during moments of production of individual phones. This study explored the relationship between intra-oral pressure and Fo during the production of the English voiced fricatives (v), (z), (o), and (3). Target words were embedded in a carrier phrase spoken with three different patterns of sentence stress. Fo changed at a mean rate of -3.59 Hz/cmH2O and -7.96 Hz/cmH2O in men and women, respectively. No significant difference was observed among the different fricatives nor among the several stress patterns. A significant sex effect, not observed in a prior related study, was eliminated by conversion of the Fo data to semitones. The observed magnitudes of the ratios of Fo change to pressure change are consistent with several earlier studies that explored the effect of passive transglottal pressure changes on Fo. The present findings imply that, although Fo regulation is involved in the generation of different intonation contours, the laryngeal system is not compensated to maintain Fo in the face of the transitory changes in vocal-tract aerodynamics that accompany voiced fricative production.