We studied the clinical and immunologic features of 10 patients with foreign body granulomatosis associated with injection of pentazocine. Five had typical micronodules on chest radiographs, 9 had abnormal 67Ga lung images, and 9 had elevated serum angiotensin-converting enzyme levels. Pulmonary function tests showed significant decreases in diffusing capacity in 8 subjects, but were otherwise normal. Bronchoalveolar lavage fluid had significantly (p < 0.02) increased total cell numbers (13.8 ± 7.5 x 107) and significantly lower percentages of lymphocytes (2 ± 1) and neutrophils (2 ± 1) (p < 0.02) when compared with that from control subjects. Peripheral blood lymphocytes were normal when expressed as percentages of total leukocytes or as percent T-lymphocytes. Monoclonal antibody determinations of T-lymphocyte subsets (helper and suppressor) were similar to those in control subjects (p = NS). Lymphocyte transformation responses to a variety of antigens and skin test reactivity were normal. Foreign body granulomatosis contrasts with other interstitial lung diseases in its bronchoalveolar lavage cellular profile and in the absence of altered peripheral immunologic indexes.