Objective: To determine age- and sex-specific population trends in fatal and non-fatal first coronary heart disease (CHD) events in Western Australia from 1996 to 2007. Design: Longitudinal retrospective population study. Setting: State-wide population. Patients All residents aged 35-84 years during 1996-2007 who died or were hospitalised with a principal diagnosis of acute CHD. Data sources: Person-linked file of mortality and morbidity records. Main outcome measures: Age-standardised (35-84 years) and age-specific (35-54, 55-69, 70-84 years) rates by gender for a first CHD event were calculated with a 10-year lead-in period to define first events. Results: From 1996 to 2007 there were 36 631 first CHD events, including 8518 (23%) fatal cases in those aged 35-84 years. Overall, age-adjusted rates for fatal first CHD declined 5.3%/year in men (95% CI -6.1% to -4.6%) and 6.5%/year in women (95% CI -7.5% to -5.5%). However, age-specific fatal first CHD rates were neutral in both men aged 35e54 years (0.1%/year; 95% CI -1.8% to 2.1%) and women of the same age, (-1.6%/year; 95% CI -5.6% to 2.5%). Age-specific trends in non-fatal CHD rates reflected the same trends in fatal CHD events in men and women, with rates reportedly increasing in women aged 35-54 years (2.5%/year (95% CI 1.1% to 3.9%). Conclusion: The age-specific decline in fatal and non-fatal first CHD rates in older men and women was not observed in those aged 35-54 years. These novel findings provide evidence for a levelling in the CHD incidence rates in younger adults and puts renewed importance on primary prevention in this group.