Head injuries in children under the age of 3 years have not been extensively studied, due in part to the lack of an objective tool for neurological assessment. We have developed a Children's Coma Scale (CCS) by modifying the verbal response subscore of the Glasgow Coma Scale (GCS) to overcome this limitation. When applied prospectively to children under 3 years of age, we found the CCS to be useful in predicting outcome. During the 5-year study period from 1981 to 1985, there were 738 patients with head injuries (0-16 years) admitted to the Children's Memorial Hospital in Chicago, including 318 (43.1%) less than 3 years of age. Initial data demonstrated the following observations. The most common mechanism of injury was a fall (75.5%). Although a brief loss of consciousness (LOC) was reported in three-fourths of the patients, prolonged LOC of more than 6 h was uncommon (16/318, 5.0%). The classically described "lucid interval" was seen in only 7 children (2.2%) and was not a reliable indicator of epidural hematoma. Post-traumatic seizures developed more commonly in children under 2 years of age (15.7%) than in older children (11.6% under 3 years of age, 9.6%, entire group), (P less than 0.001). Oculovestibular reflex and bilateral fixed dilated pupils had the most reliable correlation with outcome. Other brain-stem reflexes were less useful.(ABSTRACT TRUNCATED AT 250 WORDS)