A Prospective cohort study was carried out on all inpatients admitted to J.S.S Hospital, Mysore with complaints of bleeding per vaginum in the first trimester of pregnancy during the study period from Nov 2010 to Sep 2012. A detailed clinical examination was done to arrive at a provisional clinical diagnosis. Patients were then subjected to ultrasound examination. Clinical diagnosis and ultrasound diagnosis were correlated.One hundred and twenty cases of first trimester bleeding were evaluated by ultrasonography. Commonest cause of bleeding was abortion (81.6%) followed by ectopic pregnancy (11.7%) and molar pregnancy (6.7%). Out of 120 cases 76 cases were confirmed on ultrasonography while 44 cases were proved by ultrasonography which had been misdiagnosed on clinical examination with a disparity of 63%.Ultrasonographic diagnosis proved to be very accurate on statistical evaluation. To conclude , Ultrasound is a sensitive, cost effective and a non invasive diagnostic tool in first trimester bleeding. In the present study it has helped in establishing correct diagnosis of the clinically misdiagnosed cases apart from confirming the diagnosis in the others.