Diagnoses of VTE including PE will be found by linkage to the Swedish Patient Register of the National Board of Health and Welfare. This register comprises date of admission and discharge, and main diagnosis with up to seven contributing diagnoses. Diagnoses are recorded according to the International Classification of Diagnoses (ICD), ninth version prior to 1996 and the tenth version from 1997. Codes used were 415B, 451B, 452, 453C-D, 453W, 453X, 673C, 671D-E, 671F in ICD9 and I260, I269, I801- 3, I808-9, I822-3, I828-9, O223, O225, O871, O873, O879, O882 in ICD10.