The term "cerebral dominance" suggests that one hemisphere is leader and the other subordinate; however, cerebral dominance concerning all psychic functions is less frequent than we could suppose. Among the functions in which cerebral dominance is manifested the most notorious is the manual preference. Thus according to the hand being used for general motor activities the persons are named right-handers or left-handers; nevertheless people are less lateralized than we could suppose, and most right-handers may have hidden left-handedness. In order to obtain some data on this subject in Mexican population, a study was done in 300 university students. Of the 275 right-handers only 144 fulfilled the requirements to qualify as such after performing the complementary tests; 25 left-handers came to a mere amount of 5. The data indicate that partial lateralization is more frequent than total lateralization.