Prosthetic joint replacement is frequently used for the treatment of degenerative joint disease, rheumatoid arthritis, bone tumors and traumatic lesions. The prostheses contain such materials as titanium, cobalt and chromium. We describe a patient who, after total hip arthroplasty, developed an inguinal-pelvic mass. Fine needle aspiration revealed metallic particles, also seen on light microscopy in reactive pelvic lymph nodes. Ultrastructure was consistent with the presence of foreign particles, while energy dispersive x-ray microanalysis established the presence of chromium. To our knowledge, this is the first report of chromium-related lymph node metallosis diagnosed by fine needle aspiration. Eight years after total hip arthroplasty, a 78-year-old woman developed a right pelvic cystic mass. Aspiration drainage was performed. Smears from fine needle aspiration showed numerous macrophages with abundant, foamy cytoplasm and round nuclei without atypia. Small, birefringent particles were seen in the cytoplasm. Histopathology showed fibroconnective tissue with chronic inflammation and marked lymph node sinus histiocytosis. Within histiocytes, numerous particles were present, identical to those seen in the smears. Their nature as "foreign bodies" was confirmed by electron microscopy, and the presence of chromium was shown by energy dispersive x-ray analysis. Fine needle aspiration and polarized microscopy are excellent techniques to evaluate foreign materials in lymph nodes draining the sites of joint prostheses, thus precluding confusion with other conditions, such as metastatic carcinoma.