The purpose of this study was to investigate the occurrence and risk factors of unintentional and violence-related injuries in Finnish adolescents. The study used three different data sets. The first data was based on the Official Cause-of-Death Statistics of Finland. The study population consisted of all Finns 0-14 years of age and the outcome variable was unintentional or violence-related death in 1971-2001. The second data set was obtained from a cross-sectional survey of the Adolescent Health and Lifestyle Survey (AHLS) in 1999. A structured questionnaire including questions about unintentional and violence-related injuries, sociodemographic background, health and health behaviour variables was mailed to a sample of 12, 14, 16, and 18-year-olds in 1999. The mean ages of the respondents were 12.6, 14.6, 16.6, and 18.6 years. The questionnaire was sent to 10 883 adolescents of which 8216 returned the questionnaire (response rate 76%). The third data used in the paper V was based on longitudinal data of the Adolescent Health and Lifestyle Surveys linked to the National Hospital Discharge Register and Cause-of-Death Statistics between 1979 and 2001. The main outcomes were injury-related death and hospitalisation due to injury. Baseline data for the analyses were collected from 1979 to 1997. The baseline population consisted of 72 194 persons of which 57 297 responded in the AHLS, the response rate being 79%. The results indicated that the incidence of fatal injuries among 0-14-year-old Finns declined by 83% during the 30-year study period. The decline was almost solely attributable to the decline in unintentional injury deaths. The incidence of violence-related death did not change markedly during the study period. While fatal injuries have decreased, less severe injuries have become common among Finnish adolescents. Occurrence of unintentional and violence-related injuries was 5.5% and 1.7% per one month, respectively. Unintentional injuries were more common among boys while girls reported more violence-related injuries. Most injuries were less severe, such as sprains, strains and contusions. The main anatomical locations were the extremities in unintentional and the head in violence-related injuries. Concerning violence-related injuries, some 40% of injured adolescents reported that either they or the other party were under the influence of alcohol at the time of injury. The strongest risk factors for unintentional injury were not living with own parents, stress symptoms daily, violence occurrence and frequent participation in organised sports. The corresponding risk factors for violence-related injuries were not living with own parents, stress symptoms daily, unintentional injury occurrence and smoking. Our longitudinal data revealed that the strongest predictor of injury death was poor school success in boys and smoking in girls, while the strongest predictor of injury hospitalisation was frequent participation in organised sport in both sexes. In conclusion, unintentional injury deaths have declined markedly over the 30-year study period. The reasons for this positive development are multi-factorial, but an increased general awareness of high-risk situations (for example, increased supervision when child commutes to school or when child is near water), safer playgrounds, improved traffic safety measures such as intensive promotion of child safety seat restraints, and bicycle helmets are probably among the most important single factors. Our findings indicate that, apart from some sociodemographic factors, health and health behavioural factors in particular are associated with injuries. Overall, it seems evident that several indicators of poor health status accumulate. Although, in Finland, a self-reported sociodemographic background appears to be a less important predictor of injury, efforts supporting the well-being of families may reduce the occurrence of injuries. In planning the targeting of injury-preventive measures, health and health behavioural factors should be considered as well. Since frequent participation in organised sports is strongly related to hospital-treated injuries, clearly more attention should also be paid to sports injury prevention.