While speech synthesis research is now focussing on the generation of various speaking styles or emotions, very few studies have considered the possibility of including phonetic variations according to the communicative situation of the targeted speech (sports commentaries, TV news, etc.). This paper proposes a phonetic analysis of large French corpora to assess the influence exerted by three situational ‘traits’: read/spontaneous, media/non-media and expressive/non-expressive. It shows that some variations, like elision, tend to be more frequent in spontaneous and non-media speech, conversely to liaisons which appear more often in read and media speech. Interestingly, no phonetic variation draws a clearcut distinction between expressive and non-expressive speech. Finally, a prosodic analysis indicates that the phonetic variations are not directly correlated with the rhythmic features of their corresponding situational ‘trait’.