PURPOSE: To evaluate the usefulness of four-phase dynamic MR imaging technique by analyzing the imagingfeatures of hepatocellular carcinoma(HCC). MATERIALS AND METHODS: We reviewed four-phase dynamic MR images of 63lesions in 38 patients. MR imaging of the whole liver on gradient T1-weighted sequence was obtained at 10seconds(phase I), 35 seconds(phase II), 60 seconds(phase III), and 5 minutes(phase IV) after the start ofGd-DTPA(0.1mmol/kg) hand injection(3-4cc/sec) through the vein. We evaluated the degree of lesional contrastenhancement during each phase by comparing surrounding liver parenchyma, and analyzed signal intensity in lesionsover and less 2cm, respectively. RESULTS: The number of lesions showing high signal intensity compared withsurrounding liver parenchyma was 52(83%)during phase I, 30(48%) during phase II, 12(19%) during phase III, and 4(6%) during phase IV. During each phase, the number of lesions with signal intensity lower than that ofsurrounding liver parenchyma was 7(11%), 2(3%), 7(11%) and 21(33%), respectively. Thirty-four lesions wereenhanced only during phase I and eleven during only phase II. In tumors less than 2cm(n=40), more enhanced lesionswere during phase I(n=33) than more during phase II(n=16)(p=.0020). CONCLUSION: During each phase, four-phasedynamic MR imaging is useful for the effective detection of HCC showing varying degrees of contrast enhancement.