57Co-bleomycin scintigraphy was used to detect brain metastases in 46 patients with proven lung cancer and neurological symptoms that could be caused by brain metastases. Scintigraphy was true positive in 19 patients and true negative in 27. In 44 patients without neurological symptoms 57Co-bleomycin scintigraphy was performed to detect silent brain metastases at the time the diagnosis of lung cancer was established. Scintigraphy was false negative in one of these patients and true negative in 43. It is concluded that 57Co-bleomycin scintigraphy is a reliable method to visualize brain metastases in lung cancer patients with neurological symptoms. In our patients it was not useful to detect silent brain metastases of lung cancer.