Morphologic abnormalities of the insular cortex have been described in psychotic disorders such as schizophrenia, but it remains unclear whether these changes predate the onset of psychosis or develop progressively over the course of illness. In this study, we used magnetic resonance imaging to investigate the gray matter volume of the long and short insular cortices in 97 neuroleptic-narve individuals at ultra-high-risk (UHR) for developing psychosis [of whom 31 (32%) later developed psychosis (UHR-P) and 66 (68%) did not (UHR-NP)] and 55 age- and gender-matched healthy comparisons. We also conducted a longitudinal comparison of the insular cortex gray matter changes in 31 UHR individuals (20 UHR-NP and 11 UHR-P) and 20 controls for whom follow-up MRI data between 1 and 4 years later were available. In the cross-sectional comparison, the UHR-P subjects had a significantly smaller insular cortex compared with the UHR-NP subjects bilaterally and with the controls on the right hemisphere, especially for the short insular region. More severe negative symptoms in UHR-P subjects at baseline were associated with smaller volumes of the right long insular cortex. In the longitudinal comparison, the UHR-P subjects showed greater gray matter reduction of insular cortex bilaterally (-5.0%/year) compared with controls (-0.4%/year) or UHR-NP subjects (-0.6%/ year). Our findings suggest that insular cortex gray matter abnormalities in psychotic disorders may reflect pre-existing vulnerability, but that there are also active progressive changes of the insular cortex during the transition period into psychosis. Whether these longitudinal changes are features of the disorder or related to treatment with antipsychotic medication remains to be determined. (C) 2009 Elsevier B.V. All rights reserved.