OBJECTIVES: Studies of schizophrenia endophenotypes may help clinicians better understand the etiopathogenesis and treatment of this mental disorder. The aim of the study was to determine if retinal arteriolar or venular abnormalities are an endophenotype of schizophrenia. DESIGN: We performed a one-time cross-sectional study. MATERIALS AND METHODS: We enlisted schizophrenic patients (n = 53) hospitalized in the Department of Psychiatry, University Hospital Hradec Kralove; their mentally healthy first-degree relatives (n = 53); and unrelated, age- and sex-matched mentally healthy controls (n = 49). We recorded all participants´ sociodemographic and, if relevant, clinical variables. Retinal imaging was carried out using a digital fundus camera (FF450 + IR). Outcomes included retinal vessel calibers measured using the software application VAMPIRE. RESULTS: The study enrolled fifty-three schizophrenic patients (average age 32.1 years; males n = 38), an equal number of healthy relatives (average age 47.3 years; males n = 18), and forty-nine unrelated healthy controls (average age 32.2 years; males n = 35). Patients with schizophrenia had significantly increased retinal arteriolar diameters when compared to unrelated healthy controls (left eye p = 0.003; right eye p = 0.011) but not when compared to healthy relatives. The sizes of the retinal venules were not significantly different among the study groups. CONCLUSIONS: Our cross-sectional findings do not support the notion that retinal microvascular anomalies are an endophenotype in schizophrenia. Longitudinal studies of this subject should be included in further research.