SummaryThe influence of the day of diagnosis (weekends vs. weekdays) on outcome in patients with acute venous thromboembolism (VTE) has not been thoroughly studied. We used the RIETE database to compare the clinical characteristics, treatment details, and mortality rate at 7 and 30 days, of all patients diagnosed with acute VTE on weekends versus those diagnosed on weekdays. Up to January 2010, 30,394 patients were included in RIETE, of whom 5,479 (18%) were diagnosed on weekends. Most clinical characteristics were similar in both groups, but patients diagnosed on weekends had less often cancer (20% vs. 22%; p=0.004), and presented more likely with pulmonary embolism (PE) than those diagnosed on weekdays (52% vs. 47%; p <0.001). Most patients in both groups received initial therapy with low-molecularweight heparin (90% and 91%, respectively; p=0.01), then switched to vitamin K antagonists (72% and 71%, respectively; p=0.007). The