This study examines pressure characteristics of /p/ and /b/ as a function of position with regard to stress and position within the utterance. Eight female talkers produced utterances which varied in length from one to five disyllables. Results demonstrate the importance of utterance position for the magnitude of supraglottal pressure in stops. Except in voiceless stops found in the first words of utterances, pressure was greater in the prestressed than in the poststressed position. The pressure difference distinguishing /p/ and /b/ was reduced considerably when these stops occurred in absolute utterance-initial position. A post hoc analysis revealed that pressure increased much more slowly in initial than in noninitial stops and that /p/ and /b/ were not distinguished by the rate at which supraglottal pressure increased when these stops occurred in utterance-initial position. Finally, it was found that the pressure of stops in the first words of utterances increased as a function of utterance length, suggesting preplanning for sentence production at the respiratory level.