Purpose: Many inner ear disorders, including M áeni àere's disease, are believed to be based on endolymphatic hydrops. We evaluated a newly proposed method for semi-quantiˆcation of endolymphatic size in patients with suspected endolymphatic hydrops that uses 2 kinds of processed magnetic resonance (MR) images.Methods: Twenty-four consecutive patients underwent heavily T 2 -weighted (hT 2 W) MR cisternography (MRC), hT 2 W 3-dimensional (3D) ‰uid-attenuated inversion recovery (FLAIR) with inversion time of 2250 ms (positive perilymph image, PPI), and hT 2 W-3D-IR with inversion time of 2050 ms (positive endolymph image, PEI) 4 hours after intravenous administration of single-dose gadolinium-based contrast material (IV-SD-GBCM). Two images were generated using 2 new methods to process PPI, PEI, and MRC. Three radiologists contoured the cochlea and vestibule on MRC, copied regions of interest (ROIs) onto the 2 kinds of generated images, and semi-quantitatively measured the size of the endolymph for the cochlea and vestibule by setting a threshold pixel value.Results: Each observer noted a strong linear correlation between endolymphatic size of both the cochlea and vestibule of the 2 kinds of generated images. The Pearson correlation coe‹cients (r) were 0.783, 0.734, and 0.800 in the cochlea and 0.924, 0.930, and 0.933 in the vestibule (Pº0.001, for all). In both the cochlea and vestibule, repeated-measures analysis of variance showed no statistically signiˆcant diŠerence between observers.Conclusion: Use of the 2 kinds of generated images generated from MR images obtained 4 hours after IV-SD-GBCM might enable semi-quantiˆcation of endolymphatic size with little observer dependency.