The ability to inhibit inappropriate responses and suppress irrelevant information is a core feature of executive control. In this study, we provide a detailed analysis of prepotent response inhibition and interference in patients with schizophrenia. To further test the role of genetic factors and subclinical schizophrenia-like traits, we additionally studied clinically unaffected, first-degree relatives of schizophrenia patients and assessed dimensions of schizotypy in both relatives and healthy controls. Inhibition and interference control were assessed using a battery comprising the antisaccade, Stroop, stop signal, go/no-go, flanker, and Simon tasks. Schizophrenia patients differed from both relatives and controls in making more errors on the antisaccade task and having longer response times on the Stroop task, especially the incongruent condition. Patients also had general, that is, condition independent, increases in reaction times on the go/no-go and flanker tasks and made more errors on the flanker and Simon tasks, suggesting general performance impairments independent of inhibitory demand. Relatives were characterized by hypometric antisaccade amplitude gain despite normal prosaccades, suggesting a selective deficit in non-standard sensorimotor transformations. Schizotypy was correlated with inhibitory performance across a number of tasks in both relatives and controls. Generally, these effects were independent of verbal intelligence levels. Overall, the findings point to rather selective impairments of inhibitory control in the schizophrenia spectrum and confirm a previously observed deficit in antisaccade spatial accuracy as an endophenotype of schizophrenia.