The interaction of peak oral air pressure and peak airflow rate in the production of medial voiceless stop consonants in German is investigated and the claim that the two parameters are linearly related is considered. It was found that the two parameters behave in a similar fashion with respect to the consumption of aerodynamic energy prior to the plosive and to the degree of expiratory activity, but in a reverse fashion with respect to an increase in the rate of speech. The degree of opening of the glottis is thought to be responsible for the reverse behaviour of the parameters in this case.