The authors explored the capability of high-field-strength surface coil magnetic resonance (MR) imaging in disclosing the gross pathologic characteristics of thyroid masses (especially pseudocapsular and hemorrhagic degeneration). Twenty-four patients were examined, including 12 with papillary carcinoma, eight with adenoma, and four with adenomatous goiter. All patients underwent surgery within 2 days after MR imaging. Specimens were cut and correlated directly with MR images. The appearance of the pseudocapsule was classified into four types: A, intact and even thickness around the tumor; B, only partially present or even absent; C, intact but with uneven thickness; D, partially destroyed by tumor. MR imaging findings corresponded precisely with those of gross pathologic examination in all cases but four of adenoma. Type A pseudocapsules were found only in adenoma and type D only in papillary carcinoma. Although the number of cases in the series was limited, the authors conclude that MR images reflect gross pathologic findings well and that some characteristic findings are suggestive of benign or malignant disease.