Objective: The purpose of this study is to investigate the in vivo magnetic resonance spectroscopy features of uterine leiomyomas using long echo time and to characterize the spectral patterns of these lesions. Methods: We calculated metabolites in 15 patients with uterine leiomyomas and myometrium of 20 healthy control subjects using single-voxel proton MR spectroscopy (point resolved spectroscopy technique, TE:136 ms). Voxels were placed at the center of the uterine leiomyomas. The peak areas of creatine, choline, lipid and lactate were determined. The MR spectroscopy results of uterine leiomyomas were compared with the spectroscopy results obtained from the myometrium of healthy control subjects. Results: The characteristically obtained signal was choline, which was detected not only in 14 of the 15 leiomyomas (93.3%) but also in 18 of the 20 myometrium of control subjects (90%). The lipid signals were determined in 9 of 15 patients with uterine leiomyomas (60%) and 8 of 20 control subjects (40%). The lactate signal was obtained from six of 15 patients with leiomyomas (40%) but only two of myometrium (10%). The creatine signal was obtained from 4 of 15 patients with leiomyomas (26.6%) and 5 of 20 myometrium (25%). Among the tested parameters only lactate peak was statistically significant (p < 0.05). Conclusion: Proton MR spectroscopic imaging may be helpful for the investigation of the underlying pathophysiology of uterine leiomyomas. The presence of lactate and lipid signals in the spectrum may be a useful indicator of metabolic pathway of uterine leiomyomas. Copyright (C) 2004 S. Karger AG, Basel.