OBJECTIVE Determine microcalcifications' rule in nodular goiter, to classify those calcifications and identify US features suspect for tumoral pathology. METHODS In Endocrine Surgery Unit we ultrasonographically detected 655 patients in a period of twelve months (Jan to Dec 2005). Patients aged from 22 to 75 years. Multinodular goiter were 42% and solitary nodular 33.8%, higher than other studies, as we checked selected patients. We determined microcalcification' incidence in nodular goiter and thyroiditis and studied their correlations with tumours. We also studied other US features suspect for malignant lesions. We divided microcalcifications in four groups. Thyroiditis prevalence was 55.8%. Microcalcifications' prevalence was 32.3%, divided as follow: Type I 18.1%, type II 4%, type III 81.8%, type IV 9%. In 9% of patients was present more than one kind of calcifications. Microcalcification rate was 28.9% in inflammatory disease, 55.17% in multinodular goiter and 18, 18% in single thyroid nodules. "Suspect" microcalcifications were present in 9% of whole thyroid pathology and in 12% of MNG. The majority of microcalcifications belonged to type III and their nature is questionable. Several Authors mentioned microcalcifications as a sensitive and highly specific feature for tumour diagnosis. Microcalcifications have a 59.2% sensitivity rate and a specificity rate of 85.8-95%. Their diagnostic accuracy is 77.4%. Other us suspect features are hypoecogenicity and irregular nodule outline. CONCLUSIONS Ultrasonography remains an operator-dependent exam and it's necessary a correct interpretation of morphological data. Meticulous characterization of all ultrasonographic criteria enounced above is useful to reach satisfactory results and identify suspect lesions.