This paper investigates how speech and gestures convey stress, and how they can be used for automatic stress recognition. As a first step, we look into how humans use speech and gestures to convey stress. In particular, for both speech and gestures, we distinguish between stress conveyed by the intended semantic message (e.g. spoken words for speech, symbolic meaning for gestures), and stress conveyed by the modulation of either speech and gestures (e.g. intonation for speech, speed and rhythm for gestures).