Cardiovascular diseases are the leading causes of death in Texas and in the United States. This study determines the trend in mortality rates attributed to cardiovascular diseases in Harris County from 1980 to 1986. The region of the county that does not include the City of Houston was specifically studied. Mortality of cardiovascular diseases in these two areas follow patterns similar to that of the United States in the same time period. Both the entire county and Harris County excluding Houston show declines in cardiovascular mortality rates in the 7-year period. The populations were divided into four ethnic categories (white, black, Hispanic and "other"), and each ethnic group reported significant declines in overall cardiovascular mortality except in the "other" population, which showed an increase in the male group. Significant downward trends were noticed in the white and Hispanic population in the two major subcategories of cardiovascular diseases: diseases of the heart and cerebrovascular diseases. The black population in each geographic area studied was consistently higher in cardiovascular mortality than the other three ethnic groups observed (white, Hispanic and "other"). Knowledge of cardiovascular disease mortality rates by ethnicity, sex, and age as well as temporal changes in mortality rates within Harris County are important for health planners in continuing and implementing programs aimed at awareness, prevention, and treatment of cardiovascular diseases.