Objective: Schizophrenia is associated with increased cardiovascular mortality. The deceleration capacity of heart rate is discussed to be a predictor of mortality, more powerful than conventional measures of heart rate variability (HRV) or the left ventricular ejection fraction. The aim of this study was to determine whether patients with schizophrenia, receiving antipsychotic medication have a reduced HRV indicating an elevated mortality risk. Methods: We quantified HRV and the deceleration capacity in 24-hour electrocardiogram recordings from 28 medicated patients with schizophrenia and 28 matched controls. In addition to the evaluation of the 24-hour recording, 4-hour periods of "sleep" and "wake" recordings were evaluated separately, as activity has a major influence on HRV. Actigraphy was used to identify coherent sleep and wake phases and to ensure comparable levels of activity in patients and controls. Results: Medicated patients showed a significant reduction of the HRV. The HRV was reduced significantly according to the time domain and frequency domain measures. The deceleration capacity of medicated patients was 5.36 compared with 8.26 for the controls (p< .05). Conclusions: Heart rate deceleration capacity is significantly reduced in schizophrenic patients treated with antipsychoties and may serve as an indicator of increased cardiovascular mortality risk.