OBJECTIVE The aims of this study were to investigate trends in oral health in a cohort from late childhood through adolescence to early adulthood and to describe how the oral health of young adults was affected by their family sociodemographic characteristics, oral health status, and utilization of dental services during adolescence using life course approach. METHODS A cohort of 638 students was followed from late childhood (12 years old) through adolescence (15 years old) to early adulthood (18 years old) in Hong Kong. Dental examinations included the assessment of caries experience (DMFT score) and periodontal conditions (Community Periodontal Index, CPI) according to WHO criteria. Information on utilization of dental services, parental education attainment, and monthly household income was collected. Path analyses were performed to investigate oral health trends and the relationships between oral health (DMFT scores and highest CPI values) at age 18 years and the sociodemographic characteristics at age 12 years, oral health, and utilization of dental services during adolescence. RESULTS In 2004 and 2007, 395 (62%) and 324 (51%) subjects of the original sample were followed up when they reached the age of 15 and 18 years, respectively. The mean DMFT score gradually increased from 0.62 at age 12 to 1.52 at age 18 (P < 0.001). The proportion of subjects with calculus or shallow periodontal pockets (highest CPI score 2 or 3) also increased with age, from 58% at age 12 to 96% at age 18 (P < 0.001). The oral health trend path models showed that DMFT score and highest CPI value at age 18 years were positively associated with DMFT score and highest CPI value at younger ages (P < 0.05). Results of the two extended path models showed that household income had positive effect on the utilization of dental services (β > 0.29, P < 0.05) and the utilization of dental services had positive effect on DMFT score (β > 0.12, P < 0.05) but not for highest CPI value (P > 0.05). However, parental education attainment had no significant effect on either DMFT score or highest CPI value (P > 0.05). CONCLUSIONS Oral health status had become worse from childhood to early adulthood in the study cohort. Economic circumstance of the subjects was found to be positively related to their utilization of dental services and through this contributed to the subjects' caries experience. Oral health at younger ages was positively associated with succeeding oral health conditions.