Blood dyscrasias are rare but serious diseases. We used national death certificate data for the year 1984 to estimate the number and rate of deaths caused by four blood dyscrasias. These diseases contributed to 4,490 deaths, corresponding to a mortality rate of 18.9 per million United States population. Aplastic anemia was the most frequent cause of death, followed by thrombocytopenia, agranulocytosis, and hemolytic anemia. Mortality rates varied by age, with a small peak in young children, lower rates for ages five through 34 years, and exponentially increasing rates beyond 35 years of age. Although drug relatedness could not be reliably ascertained from our data, other surveys have estimated that approximately 30% of fatal blood dyscrasias are caused by therapeutic drugs. Assuming that 30% drug attribution also applies to the U.S. population as a whole, approximately 1,350 blood dyscrasia deaths in the U.S. in 1984 may have been caused by drugs.