To assess the usefulness of fat-saturated magnetic resonance (MR) imaging in detecting small endometrial implants, 258 pigmented lesions of endometriosis from 80 consecutive patients with histophatologically diagnosed pelvic endometriosis were compared using fat-saturated and conventional MR imaging. MR imaging was performed with a 1.5-tesla superconducting magnet with spin echo T1-, T2-, and fat-saturated T1-weighted images. Both conventional MR images and fat-saturated MR images permitted identification of almost all endometriomas > 10 mm in diameter. With conventional MR imaging, 29 endometrial implants measuring < 10mm in diameter were detected. One hundred and seven lesions were detected by fat-saturated MR imaging. However, conventional MR images demonstrated only 4 lesions among these Ill small endometrial implants that measured < 5 mm in diameter. The addition of fat-saturated MR imaging increased the detection rate to 55 of Ill lesions. Fat-saturated MR imaging can, therefore, be useful in detecting small endometrial implants.