Introduction: In subjects with recent onset schizophrenia brain alterations have been found such as a decrease in cerebral grey matter and ventricular enlargement. In animal models maternal immune activation can cause neuropathological changes in offspring. Many studies have pointed out the role of inflammatory markers in schizophrenia. A common marker for inflammation is the erythrocyte sedimentation rate (ESR). Aim: To investigate whether subclinical inflammation measured by increase in the ESR is associated with a change in brain structures in subjects with recent onset schizophrenia. Method: We included 126 subjects with recent onset schizophrenia, without clinical inflammation, who underwent T1-weighted magnetic resonance imaging. Surface-based analysis was used to measure the volume of a priori based regions of interest. Venous blood was taken upon admission. We used a linear regression model with the volume of the region of interest as dependent variable and ESR, age and gender as predictors. Results: A significant positive correlation was found between the size of the third ventricle and ESR, corrected for age and gender ( p a priori regions of interest. Conclusion: The findings of this study show that in patients with recent onset schizophrenia subclinical inflammation (measured by ESR) was significantly associated with enlargement of the third ventricle. This partially confirms brain alterations found in animal models by prenatal immune activation.