Magnetic resonance imaging of small hepatocellular carcinoma. Thirty-eight patients with small hepatocellular carcinomas (HCCs), size less than 20 mm, initially detected by ultrasound (US) and histologically confirmed, were examined by magnetic resonance (MR) imaging, computed tomographic (CT) scan, and angiography. MR imaging demonstrated HCC nodules in nine (75.0%) of 12 patients with tumors less than 10 mm in diameter and in 22 (84.6%) of 26 patients with tumors 10-20 mm in diameter. In total, HCC nodules were detected in 31 of 38 patients (81.6%) by MR imaging. On the other hand, HCC lesions were found on CT scan in 14 of 26 patients (53.8%) and in 27 of 35 patients (77.1%) by angiography. With MR imaging, HCC nodules were demonstrated in 21 of 31 patients on both T1 and T2 weighted images, and 13 of 21 patients (61.9%) were shown to have low intensity areas or iso intensity areas on T1 weighted image, whereas the other eight patients (38.1%) were shown to have high intensity areas. All 21 patients were shown to have high intensity areas on T2 weighted image. Among 15 resected cases, four patients had a high intensity area on T1 weighted image, and a significant fatty change was noted in HCC nodules by histological study of the resected specimen. We suggest that MR imaging is a useful diagnostic imaging modality, even in small HCC of less than 20 mm. 