Disfluencies such as self-repairs, filled pauses (e.g. 'um') and silent pauses are pervasive in dialogue, but there is no consensus as to whether they reflect internal production pressures, or interactive issues -- or how their effects are manifest in dialogue. It is well-known that patients with schizophrenia have problems with language and social cognitive skills, yet little research has investigated how these impact interaction. We report a study on the disfluency behaviours of patients with schizophrenia and their interlocutors who were unaware of the patient's diagnosis, compared to healthy control groups. Results show that patients use fewer self-repairs than either their partners or controls and fewer filled pauses ('er', 'um') than controls. Furthermore, the presence of the patient also affects patients' partners, who use fewer filled pauses than controls and more unfilled pauses than both patients and controls. This suggests that smooth coordination of turns is problematic in patients' dialogues.