In a prior prospective study, we evaluated the nature and rates of adverse reactions occurring within 48 hours following 15,752 diphtheria-tetanus-pertussis (DTP) immunizations. Nine children had convulsions, and nine had hypotonic-hyporesponsive episodes. After an interval of 6 to 7 years, we were successful in contacting the families of 16 of these children to determine whether any had evidence of neurologic impairment too subtle to have been detected at the time of initial evaluation. All 16 were considered normal by their parents and were doing well in school. A complete neurologic and psychometric evaluation was performed on 13 of these children. No child had significant neurologic deficit, although four had minor neurologic abnormalities. Psychometric testing revealed normal performance IQ scores (104.3 +/- 15.8) but low verbal IQ scores (91.8 +/- 18.4); however, these lower verbal IQ scores can be explained by the proportion of Hispanic and bilingual children in this sample. Therefore, there is no evidence that any of these 16 children have any serious neurologic damage as a result of a convulsion or a hypotonic-hyporesponsive episode temporally associated with a prior diphtheria-tetanus-pertussis immunization.