Surgical patients are at high risk for developing deep vein thrombosis (DVT). There are many reports concerning DVT, but little is known about silent deep vein thrombosis (sDVT). This study aimed to determine the incidence of sDVT. Secondary objective is to identify the associated factors for the use of DVT prophylaxis and Caprini risk scores among major surgery patients. This prospective observational study involved postoperative surgical patients who are at risk of developing sDVT. The Caprini risk-assessment scores were calculated, and each subject had a preoperative and postoperative compression ultrasound complemented by duplex venous ultrasonography of deep venous system. No patient from the study experienced sDVT. There were significant associations between Caprini risk score group (odds ratio, 8.16; 95% confidence interval [CI], 1.01-68.74; P = .016) and the use of central venous catheter (odds ratio, 6.34; 95% CI, 1.62-24.80; P = .008) with DVT prophylaxis. Interestingly, the use of central venous catheter resulted in more than four-point increment of Caprini risk scores (mean increment, 4.19; 95% CI, 3.16-5.21; P