This quantitative MRI study reports measurement of corpus callosum area tak
en from midsagittal brain images in 51 healthy men and 41 healthy women, sp
anning the adult age range (22 to 71 years). Men had larger brains acid cor
pora callosa than women, but callosal size did not correlate with age in ei
ther sex. Intracranial (i.e.) volume (ICV) and midsagittal i.c. area (ICA)
of brain were used in covariate, regression, and ratio analyses to determin
e whether sex differences in the corpus callosum endured with statistical a
djustment fur sex differences in maximally attained brain size. With the ex
ception of one ratio measure, the different statistical adjustments for the
contribution of sex differences in brain size to corpus callosum size all
indicated that men had larger corpora callosa than women for their brain si
ze. A subsample of men and women selected to be matched on i.c. volume and
age confirmed this statistical observation. Sexual dimorphism in the corpus
callosum is not a simple artifact of sex differences in brain size and may
reflect differences in connectivity necessitated by differences in brain s
ize. (C) 2001 Elsevier Science Inc. All rights reserved.