Bone marrow examination is commonly included in the staging of small cell lung carcinoma (SCLC). We reviewed marrow samples of 103 patients. Marrow examination was mainly performed by unilateral or bilateral biopsy of iliac crests, using a Jamshidi needle. Only 6 of 97 evaluable cases (6.2 per cent) were positive for marrow metastases at staging, and in 3 cases (3 per cent) bone marrow was the only metastatic site. No focal metastases were found in additional sections made from the blocks of negative samples. In our experience bone marrow biopsy was of little value in staging SCLC. Bilateral biopsy plus aspirate, with the addition of more sophisticated staining techniques might, however, provide a higher yield of positive marrow involvement.