A review of 14,667 necropsy reports for every year from 1965 to 1990 and 6,436 diagnostic venograms performed from 1976 to 1990 was undertaken at a single teaching hospital. A progressive reduction in the percentage of necropsies reporting fatal pulmonary embolism from 6.1 to 2.1%, occurred over the 25-year period (chi(2) tests for linear trend with time p < 0.00001). Over the last decade, there has been a significant reduction in the rate of venographically diagnosed postoperative deep vein thrombosis (DVT) from 49.9 to 24.7 per 100,000 population (p < 0.0001) which was in marked contrast to the constant rate of non-postoperative DVT. Our findings suggest that the introduction of thromboprophylactic measures, in addition to changes in hospital practice, may have had a highly significant effect on the pattern of this serious, but potentially avoidable disease.