Introduction: USG guided FNAC of thyroid particularly facilitates accurate FNAC of non-palpable small lesions. It has the major advantage of real time monitoring which help in accurate localisation of needle tip during aspiration. It is very useful in the non diagnostic or unsatisfactory cases (according to Bethesda System Bethesda category I). It has been suggested to reduce the rate of non-diagnostic material and subsequently reduce the false-negative interpretation. Aims: 1) To evaluate the Diagnostic accuracy of USG-guided FNAC of Thyroid. 2) To evaluate cellular yield of aspirated material in USG-guided FNAC. Materials and Methods:The present study included 100 patients with thyroid swelling undergoing USG guided FNAC who previously were diagnosed by FNAC as Non diagnostic or Unsatisfactory (According to Bethesda System Bethesda category I). USG guided FNAC was done & Smears were made. Then microscopy was done following the Bethesda system (TBS). Result: Total 100 patients with thyroid swelling undergoing USG guided FNAC who previously were diagnosed by FNAC as Bethesda category I. In present study, Out of 100 patients, maximum no. of patients were in 41 to 50 years age groups (54 cases) and majority were Female (84 Cases). The revised diagnosis in these cases according to TBS were as follow, Nodular goiter (29%), Colloid goiter (26%), lymphocytic thyroiditis (14%), Hashimoto thyroiditis (9%), Graves' disease (2%) & granulomatous thyroiditis (1%). Suspicious for malignancy (4%) and papillary carcinoma (4%) and Follicular neoplasm (3%). There was increased cellular yield of aspirated material in 92% of cases with USG guidance. In present study false negative & True Positive rates were-92% & 8% for Conventional FNAC technique, as concluded after repeat FNAC under USG guidance.