Among US adults with diabetes, using data from the National Health and Nutrition Examination Survey for 1971-1974, 1976-1980, 1988-1994, and 1999-2000, the authors describe 30-year trends in total cholesterol, blood pressure, and smoking levels. Using Bayesian models, the authors calculated mean changes per year and 95% credible intervals for age-adjusted mean total cholesterol and blood pressure levels and the prevalence of high total cholesterol (> or =5.17 mmol/liter), high blood pressure (systolic blood pressure: > or =140 mmHg and/or diastolic blood pressure: > or =90 mmHg), and smoking. Between 1971-1974 and 1999-2000, mean total cholesterol declined from 5.95 mmol/liter to 5.48 mmol/liter (-0.02 (95% credible interval: -0.03, -0.01) mmol/liter per year). The proportion with high cholesterol decreased from 72% to 55%. Mean blood pressure declined from 146/86 mmHg to 134/72 mmHg (systolic blood pressure: -0.5 (95% credible interval: -1.1, 0.5) mmHg per year; diastolic blood pressure: -0.6 (95% credible interval: -1.0, -0.03) mmHg per year). The proportion with high blood pressure decreased from 64% to 37%, and smoking prevalence decreased from 32% to 17%. Although these trends are encouraging, still one of two people with diabetes has high cholesterol, one of three has high blood pressure, and one of six is a smoker.