Oral contraceptives (OC) are a definite risk for venous thrombosis. It is commonly accepted that they cause a fourfold increased risk of thrombosis compared to non-users. The prescription patterns were evaluated from 1990 to 2000 in a northern Italian province (province of Padua). This province is typical of other northern Italian provinces. As a consequence, it can be safely assumed that the observations gathered may apply to the entire north of Italy. During these years, a sharp increase in the use of OC was noted. Furthermore, around 1995 to 1996, a marked switch toward the use of preparations containing third-generation progestins was noted. During the past few years of the observation period, approximately 80% of women use preparations containing third-generation progestins. During the same period, an increased incidence of episodes of venous thromboembolism (VTE) was noted. The increase in the prevalence of VTE episodes appeared to be proportional to the increased use of OC, regardless of the type of progestin contained in the oral contraceptive preparations.