Twenty patients with mild and, in a few cases, moderately severe head injuries were examined 3 days and 1 month postinjury. The results indicate that these patients, as compared to appropriate controls, show significant neuropsychological difficulties at 3 days, but not at 1 month postinjury. Postconcussional symptoms are endorsed, on the other hand, at both 3 days and 1 month. Absence of significant neuropsychological findings at 1 month is contrary to some of the previous reports. A number of reasons for this discrepancy were discussed. Some of these included: (a) inappropriate controls used in previous research; (2) failure to screen for pre-existing conditions in prior studies, therefore confounding the effects of the injury with pre-injury factors; (3) possible practice effects in our research; and (4) differences in the neuropsychological measures used across different studies.