A review of records of 18,104 Charnley low-friction arthroplasties, performed during a 17-year period, shows a 0.7% incidence of fatal pulmonary embolism. Ninety percent occurred within four weeks of surgery and 71% were submitted to postmortem examination. There was a strong seasonal variation. The incidence from November through February was 1% as compared with 0.42% for the remainder of the year. The difference was statistically significant at 0.01 greater than p greater than 0.001 level. There was no significant seasonal variation in deaths from other causes.