Relative brain sizes, based on actual measurement of the brains of nin
e species of myomorph rodents, two insectivores and a macroscelidid ar
e reported. Relative brain sizes of the macroscelidid and Tatera leuco
gaster were far larger than those of the other rodents. With the excep
tion of T. leucogaster, relative brain sizes were largest in semi-arbo
real, omnivorous and nocturnal rodent species.