MANY CURRENT neurological texts continue to recommend the inclusion of the serial sevens test (counting backward from 100 in sevens) in neurologic examinations of the mental function of patients with suspected or confirmed brain lesions. Hayman1 (1942) administered this test to 580 adult psychiatric patients and concluded that it was a quick and reasonably accurate test for assessing intellectual efficiency or deterioration in patients with psychiatric and neurologic disorders. Hayman also compared patterns of errors of the adult psychiatric patients with errors of 433 normal male and female school children between the ages of 8 and 15 years, and he described four identical patterns of errors in the two populations. However, the origins, rationale, and validity of this now conventional neurological test have rarely been reviewed. In 1966, Luria2,3 described serial sevens as an important neurologic diagnostic aid in many cases because This test makes particularly high