Background: Important discovered of incidental thyroid nodules by different imaging like CT or MRI and examination of the nodules by ultrasound to differentiate between the benign and malignant thyroid nodules and assess the vascularity of the nodules by color Doppler.  Aim of work: The study was done to evaluate the role of US examination and color Doppler in assessment of incidental thyroid nodules Patient and methods: We evaluated 50 patients (by ultrasound and color Doppler) with 36 benign thyroid tumors,14 malignant thyroid tumors. The ultrasound and color Doppler diagnosis was confirmed by histological examination. Results: In this study the US diagnosis was correlated with the final diagnosis based on histological examination in 92% of cases, 14 cases 28% were malignant and 32 cases 64% were benign. Conclusion: US is a valuable tool in assessment of incidentally detected thyroid nodules in others imaging features as it can show specific morphologic pattern in differentiating benign form malignant nodules. Ultrasonography can shorten the diagnosis time and reduce the burden on physicians. US diagnosis was correlated with the final diagnosis based on histological examination in most cases.