Background: Venous thrombosis is a major health problem. It is predominantly a disease of older age. The study was conducted to determine the epidemiological factors of venous system thrombosis in southern Rajasthan. Material & Methods: The prospective observational cohort study design adopted the epidemiological factors of venous system thrombosis in southern Rajasthan. The study was conducted among 100 patients. Various invasive and noninvasive radiological investigations and hematological investigations were done. The patients were followed up till the time of discharge and hospital outcomes. Results: Among male most patients were from 31-50 years age group and among females most of them from 18-30 years age group. Mean age was 24 years. Male predominance for venous thrombosis was found in the study and 66% patients were males and 34% patients were females. Male to female ratio was 2:1. Of the 100 patients enrolled in study there was 1 case of subclavian vein thrombosis and 3 cases of superior venacava thrombosis. Rest maximum cases were either DVT or CVST. None of the patients presented with IVC thrombosis. All of them underwent all investigations as per protocol and also there was no mortality. In our study, maximum cases were DVT i.e. 50% followed by CVST i.e. 30% followed by PVT and SVT. Among males’ maximum patients had DVT I.E. 50% among females maximum patients had CVST i.e. 30%. Conclusion: The present study concluded that Venous System Thrombosis found mostly among male patients of age group 31-50 years and among females most of them from 18-30 years age group. Male to female ratio was 2:1. Maximum cases were DVT i.e. 50% followed by CVST i.e. 30% followed by PVT and SVT. Among males maximum patients had DVT i.e. 50% and among females maximum patients had CVST i.e. 30%.