Abstract : Carpal tunnel syndrome (CTS) is the most common compression neuropathy caused by the compression of median nerve in the carpal tunnel. Nerve conduction study is the gold standard investigation for the diagnosis of carpal tunnel syndrome. Ultrasonography is now considered an important diagnostic tool in carpal tunnel syndrome. The current study aimed to evaluate the role of ultrasound in the detection of CTS in the study population. A total of 42 patients with clinical suspicion of carpal tunnel syndrome were included in the study. The patients underwent both NCS and ultrasonography. The Cross sectional area (CSAc) of the median nerve was measured at the pisiform, the flattening ratio at the level of hook of hamate, and the CSAp at the level of proximal third of pronator quadratus was measured and we calculated ΔCSA (CSAc- CSAp). Loss of normal echogenicity of the nerve with diffuse hypoechogenicity was also considered for the diagnosis of CTS. ΔCSA with a threshold of 2mm2 showed the highest sensitivity and specificity to diagnose CTS in our study population. It had a sensitivity of 94.3% and specificity of 100%. The CSA of the median nerve at the pisiform had a sensitivity of 94.3% when a cut-off value of 10mm2 was used. The mean CSA at pisiform among the study population was 12.88mm2 with a standard deviation of 3.74. The sensitivity of the flattening ratio in diagnosing carpal tunnel syndrome was 31.4% and the sensitivity of nerve edema (nerve hypoechogenicity) was 54.2%. We conclude that ultrasonography could be considered a cheap and non-invasive diagnostic modality for the initial assessment and early diagnosis of idiopathic carpal tunnel syndrome. High frequency ultrasound can demonstrate anatomical changes in the median nerve occurring due to compression within the carpal tunnel. Among the 4 ultrasound parameters, ΔCSA was found to be the most useful ultrasound parameter to diagnose carpal tunnel syndrome.