We investigated judgements of agency in participants with schizophrenia and healthy controls. Participants engaged in a computer game in which they attempted to touch downward falling Xs and avoid touching Os. On some trials, participants were objectively in perfect control. On other trials, they were objectively not in complete control because the movement of the cursor on the screen was distorted with respect to the position of the mouse by random noise (turbulence), or it was lagged by 250 or 500 ms. Participants made metacognitive judgements of agency as well as judgements of performance. Control participants' judgements of agency were affected by the turbulence and lag variables-indicating that they knew they were objectively not in control in those conditions, and they were also influenced by their assessments of performance. The patients also used their assessments of performance but neither turbulence nor lag affected their judgements of agency. This indicated an impairment in agency monitoring. The patients, unlike the healthy controls, used only publically available external cues about performance in making judgements of 'agency' and did not rely on any additional access to internal self-relevant cues that were diagnostic in indicating whether or not they were, in fact, in control.