Background: FNAC is useful tool to evaluate dominant thyroid nodule in patients with multi nodular goiter however, because the diagnostic performance of US-based FNAC criteria varies according to the individual international society guidelines, clinicians should be aware of the strengths and weaknesses of US-based FNAC criteria in the management of dominsnt nodules in patients with multinodular goiter. FNAC is an office procedure, done with or without local anesthesia with 23 to 27 gauge needle, to obtain cells samples for cytological examination. It is a safe, accurate and cost-effective way for evaluating dominant thyroid nodules. Objective: the aim of this study was to discuss the accuracy of Ultrasound guided FNAC technique in diagnosis of pathological types of dominant nodule in multinodular goiter. Patients and Methods: this was a prospective study to evaluate the accuracy of FNAC in diagnosis of pathological type of dominant nodule in 20 patients with multinodular goiters who referred to the endocrine surgery unit at El-Demerdash Hospital, Ain Shams University from March 2017 to December 2017. Results: in our study the FNAC results indicated malignancy in 1 patients (5%), benign in 13 patients (65%) and intermediate in 6 patients (35%). The final histopathological diagnosis was malignancy in 3 of the patients (15%); one case had follicular thyroid carcinoma while two of the patients had malignant papillary thyroid tumor. Among the rest, 17 patients (85%) had benign lesion or tumor. Out of the 13 cases identified to be benign lesion by thyroid FNAC 7.7% of the group subjects were found to be malignant follicular carcinoma by biopsy (N=1). Conclusion: the main problem among the clinical features is false negatives, as it implies the presence of undetected carcinomas. Although FNAC is useful test, our decision making should not be depend on the basis of its results and sometimes clinical and U/S criteria are preferred to cytological data.