OBJECTIVE To see the diagnostic yield of color Doppler ultrasonography in patients who presented with clinical symptoms and signs of acute deep vein thrombosis of lower limb. METHODS Descriptive study. METHODS The study was carried out in Bolan Medical Complex Hospital, Quetta from January 2002 to December 2002. METHODS Twenty five patients, who presented with clinical symptoms and signs of acute deep venous thrombosis of lower limb, were selected. In all patients color Doppler ultrasound and venography was performed to compare the results. RESULTS The age of the patients ranged from 16-82 +/- 20.33 years. The mean was 49.16, median 50.00 and mode 60.00 There were 15 females (60.00%) and 10 males (40.00%). Left lower limb involvement was seen in 12 patients (48.00% +/- 0.51), right lower limb involvement in 10 patients (40.00% +/- 0.50) and both limbs involvement in 3.0 patients (12.00% +/- 0.33). Color Doppler ultrasound was positive in 16 patients (64.00% +/- 0.48) while venography was positive in 21 patients (84.00% +/- 0.37%). Doppler ultrasonography and venography showed that 11 patients (52.38%) had distal DVT, while 10 patients (47.62%) had distal as well as proximal DVT. Ten patients (100.00%) of proximal as well as distal DVT were diagnosed by CDU and later confirmed by venography. Eleven patients (100.00%) of distal DVT only in whom 6 patients (54.54%) were diagnosed by CDU, while 5 patients (45.46%) had inconclusive findings, which were confirmed by venography. Doppler ultrasonography compared venography showed sensitivity 76.1%, specificity 100%, positive predictive value 100%, negative predictive value 44.45% and accuracy 80.00%. CONCLUSIONS Color Doppler ultrasonography is a non-invasive, safe, efficient and cost-effective method in diagnosing acute deep venous thrombosis of lower limb but still it has not 100% accuracy. It is better for diagnosing proximal DVT than distal DVT. 7.