The talk focuses on inter-speaker variability in speech production and on its potential links with biomechanical and morphological characteristics of the oro-facial speech production system. To do so we will first present data from the literature and analyze how the observed variability informs about biomechanical factors or can be linked to them. Second, using a biomechanical model of the jaw-tongue system we will analyze how biomechanical factors such as vocal tract and head morphology, muscle force directions and soft tissue stiffness can affect speech movement amplitudes, trajectories, and accuracy.