PURPOSE: To correlate signal intensities of hepatocellular carcinomas on MR images with applied field strength, tumor vascularity, history of transarterial chemoembolization, and their histopathologic findings. MATERIALS & METHODS: Twenty-two tumors in 18 patients with histologically proved hepatocellular carciomas were examined by MRI at 0.5T(14), 1.5T(5), or 2.0T(3). Tumor size ranged from 1 cm to 10 cm. We analyzed the signal intensities, presence of pseudocapsule and mosaic pattern of hepatocellular carcinomas on TI-, T2- and heavily T2-weighted images, and correlated them with histologic type and grade, as well as tumor vascularity on hepatic arteriography. RESULTS: Signal intensities of the tumors were hyperintense(6), isointense(11), or hypointense(5) on Tl-weighted images, hyperintense(21) or isointense(1) on T2-weighted images, and hyperintense(15) or isointense(3) on heavily T2-weighted images. There were hypointense tumors(3/13) on Tl-weighted MR images at 0.5 T, whereas they were absent at 2.0 T(0/4). Only one tumor was avascular which was hyperintense on Tl-weighted images. Capsules were present in 13 cases and Tl-weighted images depicted them in 10 cases, while T2-weighted images depicted them in 8 cases. Mosaic patterns with inhomogeneous signal intensity were present in 15 cases, and were seen in 7 cases on Tl-weighted images whereas 11 cases on T2-weighted images. Mixed trabecular and pseudoglandular patterns of histologic growth were seen in 5 tumors. On MR images, trabecular portion was seen as hypointense area on Tl-weighted images and hyperintense on T2-weighted images. Pseudoglandular portion was seen as isointense or hyperintense area on Tl-weighted images and as marked hyperintense and on T2-weighted images. Mixed cytologic feature of classic and clear cell was found in 4 tumors and three of these 4 cases were hyperintense on Tl-weighted images. Four of the six tumors with grades I-II were hyperintense on Tl-weighted images. Tumors with grades II-Ill, Ill-IV were 14 cases, and only two of these cases showed hyperintensity on Tl-weighted images. Peliotic change was present in one case, and was seen as hyperintense foci on T2, & heavily T2-weighted images. CONCLUSION: Pathologic correlation suggest that hyperintensity on Tl-weighted images might be due to pseudoglandular pattern, low grade of malignancy or clear cell portion of hepatocellular carcinoma. Marked hyperintensity on T2-weighted images may be due to pseudoglandular pattern or peliotic change.