Computer-assisted tissue classification based on MR intensity values in spin echo and inversion recovery images were used for area measurements of different brain structures in 76 apparently healthy volunteers of various ages. The classification was made from transaxial sections through the basal ganglia and discriminated between brain tissue and cerebrospinal fluid. The measurements based on this discrimination demonstrated larger intracranial areas in men than women. In the total group, sex differences were not observed when the measured structures were corrected for interindividual differences in cranial size. In subjects older than 60 years relative lateral ventricular area was larger and relative brain area smaller in men than women. The lateral ventricles, the Sylvian fissures and the brain area showed the most marked relation to age. The age-relation was more marked for left hemispheric structures.