Various disease processes such as inflammation, hemorrhage and tumor may follow various tissue planes to spread to a distant site. Thus pelvic diseases may present in the perineum, buttocks, hips or lower extremities. In the same way, disease outside the pelvis may extend into the pelvis. This report collected 12 such cases, including 10 with tumor and 2 of inflammation. All had computed tomography (CT). Six cases showed spread through the iliopsoas route, 3 through sacrosciatic route and 2 through obturator foramen route. One case showed tumor extending through both the iliopsoas and obturator foramen routes. Findings on radiographs and contrast studies (urogram and barium enema) are of limited value in the absence of subcutaneous emphysema and contrast extravasation. CT is very helpful in detecting both the intrapelvic and extrapelvic lesions and clearly defines the pathway of connection between both processes. Accurate diagnosis of such cases, especially with occult pelvic disease, facilitates prompt and appropriate therapy and may significantly alter therapeutic planning.