Nineteen patients with newly diagnosed small cell lung cancer (SCLC) were examined with a nanocolloid Tc-99m bone marrow whole body imaging (scintigraphy) in order to detect bone marrow metastasis. Bilateral bone marrow biopsy taken from the posterior iliac crest was used as a reference. The scintigraphy was considered abnormal if a focal lesion was present and/or if the bone marrow activity expanded to more than one-third of the proximal part of the extremities. In 3 of the 19 patients, microscopical bone marrow metastasis and cold spots (focal lesions) on the scintigram were present. An additional 9 patients had expansion of the activity. Eight patients showed scintigraphic focal lesions in the liver. SCLC metastasis was confirmed in 4 patients, while 1 patient had focal necroses. The results indicate that cold spots rather than expansion of activity with bone marrow scintigraphy detected bone marrow involvement of the disease in patients with SCLC.