Trends in chronic diseases provide insights into strategies required to improve population health. The authors determined prevalence and multiple-adjusted population attributable risk (PAR) estimates of chronic diseases because of lifestyle factors among Australian adults between 1989-90 and 2004-5, accounting for demographic factors. Between 1989-90 and 2004-5, prevalence increased for diabetes (3.8-6.0%, P < 0.001) and high cholesterol (11.3-13.9%, P < 0.001), but decreased for high blood pressure (21.4-20.4%, P = 0.003) and cardiovascular disease (CVD, 6.2-5.4%, P < 0.001). Prevalence increased for body mass index (BMI) 25-29.9 (30.3-34.9%, P < 0.001), BMI 30-34.9 (7.4-13.5%, P < 0.001) and BMI 35+ (2.1-5.4%, P < 0.001), but decreased for metabolic equivalent-hours per week (MET-hr/week) 0 (36.8-33.1%, P < 0.001) and current smokers (27.6-24.4%, P < 0.001). Diabetes, high cholesterol and high blood pressure burden increased mostly for 60+ years, lowest income quintiles and high BMI (30-34.9 and 35+). Diabetes and CVD burden increased mostly for MET-hr/week 0. Many chronic disease cases would have been theoretically prevented if adults had no prior exposure to BMI 25-29.9 (PAR 9-17%), BMI 30+ (PAR 1-14%) and MET-hr/week 0 (PAR 6-14%). Reducing exposure to lifestyle hazards across the lifespan is required for reversing the rising burden of chronic diseases. Decreases in CVD and high blood pressure prevalence were likely due to targeted improvements in health care, indicating that more can and should be done.