Abstract: An optical localization fiber 20 is provided suitable for preoperative localization of soft tissue lesions by x-ray mammography, CT, MRI, ultrasonography, or nuclear medicine. A hook 28 is carried by the optical fiber for retaining the fiber in soft tissue. The tip 26 of the optical fiber is visible through the soft tissue when the proximal end of the optical fiber is attached to a light source 170. Other embodiments include clad or coated 42 optical fibers, bundled optical fibers 156, hooks which are metallic 82, braided 66, and multiple 128, and a helix 162.