This study explores the differences between the aerodynamic characteristics of onset and coda fricatives. Such differences may account for the weakening of syllable-final fricatives found synchronically and diachronically in a variety of languages. Simultaneous oral pressure, airflow, and audio-signal were obtained for two English speakers. Aerodynamic and acoustic analyses showed that, in comparison with onset fricatives, coda fricatives exhibit (i) a slower oral pressure build-up, (ii) a lower pressure peak, (iii) a delayed onset of audible frication, and (iv) lower intensity of frication. In order to provide high flow for frication, voiceless coda fricatives show earlier glottal opening (i.e., a larger increase in flow at the VC transition) than onset fricatives, suggesting compensatory strategies. The findings suggest that modification of the aerodynamic conditions - velocity and duration of flow through the oral constriction - due to a decreased oral gesture syllable-finally and/or lowered subglottal pressure utterance-finally (and possibly coarticulation with conflicting segments) make audible friction more difficult for speakers to produce and for listeners to detect, leading to final fricative weakening or loss. © 2010 Elsevier Ltd.