Little is known about risk factors related to traffic injuries (RTI) to child pedestrians or bicyclists. Virtually all previous studies have been retrospective in design and suffer from reporting bias. This study is based on a secondary analysis of a large cohort of children born in Britain in 1958. Data about possible risk factors related to medical, developmental or psychological abnormalities and those pertaining to scholastic attainment and family factors, were assessed by home interviews, medical examinations, and teacher ratings at ages 7 and 11. Subsequent injuries in traffic were recorded at ages 11 and 16. Of the 13,634 on whom data were available at age 11, 430 or 3.2% had a traffic injury - twice as many boys as girls and twothirds were hospitalized. At age 16, data were available for 11,507 children of whom a further 662 or 5.8% had experienced their first RTI after age 7. Again the sex ratio was nearly 2:1, M:F. There were no significant social class trends in either age group. The following odds ratios for risk factors were statistically significant in the 811 age group: scruffy appearance (1.7); less than average reading score (1.8); low education of father (1.4); housing problems (1.6); and abnormal personality rating or scores indicative of maladjustment on standardized scores (1.7). In the 12 to 16 age group a similar constellation of risk factors were identified: very thin size (2.4); poor coordination (2.1); poor math score (1.9); crowding (1.4); child in foster care (2.0); and behavioral problems (1.8). When these factors are combined the cumulative risk for 7-11 boys is increased by a ratio of nearly 7 when they are characterized as both "never still" and "scruffy" in appearance. For 1216 year old boys, the combination of poor arithmetic scores, poor coordination, and overcrowding again yields a risk ratio of 7.0. These results are discussed in relation to both methodologic issues and with respect to their possible contribution to an understanding of etiology.