Data from 6695 men and women of ages 30, 40, 50, and 60 years, examined in the Danish WHO MONICA surveys in 1982-84, in 1986-87, and in 1991-92, were analyzed to estimate secular trends in body height and weight, blood pressure, and serum total, HDL-, and LDL-cholesterol, and triglyceride. Body height increased 0.1% per year, and body mass index increased 0.4% per year in women. Diastolic blood pressure increased 0.4% per year in women and 0.6% per year in 60-year-old men. HDL cholesterol declined 0.4% per year. Body mass indices in men, diastolic blood pressures in men <60 years of age, systolic blood pressures, total- and LDL cholesterol and triglyceride did not change. The levels of biological risk factors in the Danish WHO MONICA study population did not show trends during the 1980s that help explain the declining incidence of myocardial infarction in the population.