Percutaneous aspiration biopsies of opacified retroperitoneal lymph nodes, and retroperitoneal, intraperitoneal and paraspinal masses were successfully accomplished in 14 of 17 patients. A 23 gauge needle was utilized for the procedure which is performed under fluoroscopic guidance. Metastatic carcinoma, sarcoma and melanoma were identified by aspiration biopsy while the diagnosis of lymphoma, especially as to type, was more difficult. No significant complications resulted from passage of the needle through the peritoneal cavity.