Recent imaging studies in Tourette's syndrome (TS) have reported a loss of normal asymmetry in basal ganglia volumes. Our recent report of reduced midline sagittal cross-sectional area in TS suggests that altered lateralization may be widespread throughout the TS cerebrum. We report here our analyses of cerebral asymmetries of T2 (transverse or spin-spin) relaxation times derived from multi-echo/multi-planar/spin-echo magnetic resonance images in 14 adult TS subjects and 14 matched normal control subjects. T2 relaxation times were found to be asymmetric throughout the cerebrum of normal control subjects, with differences seen between T2 times of corresponding regions of both cerebral hemispheres that were small in magnitude (2-5%) but of a high degree of statistical significance in all regions examined. Our hypothesis of altered T2 relaxation time asymmetries in TS was confirmed in a multivariate analysis of variance, with post hoc analyses suggesting that group differences were attributable to specific asymmetry differences in the TS insular cortex and frontal white matter. Exploratory analyses revealed group differences in T2 times of the amygdala and red nucleus, as well as significantly lower ferritin levels in the TS group. These findings are discussed in relation to the previous TS volumetric studies, and the tissue characteristics that might produce normal and abnormal relaxation time asymmetries are considered.