This antibody allows the identification of a 145 Kd c-kit (CD117) gene product which is inserted in the cellular plasma membrane of human glioblastoma cells, and also immunohistochemically recognized the c-Kit gene products in various human solid tumours as well as in fetal and adult normal tissues. In the present study, 56% of small cell lung carcinoma and 75% of large cell lung carcinoma have shown the positive staining, whereas squamous cell carcinoma and adenocarcinoma have showed the low immunoreactivity (19%). On the other hand, c-kit expression could not be observed in fetal and adult lung tissues. Contrary to the lung, c-kit products were highly expressed in normal mammary glands, whereas low c-kit expression was observed in breast cancers. Some results suggest that the c-kit gene products may be closely related to the process of malignant transformation and to the pathogenesis of some specific types of human solid tumours such as small cell lung carcinoma.