Tests were performed to study the angiogenic activity in samples of pleural fluid, ascites and cerebrospinal fluid, in patients with solid tumors and non‐neoplastic diseases such as cerebrovascular accidents, cirrhosis, and congestive heart failure. The measurement of the angiogenic activity was carried out on chorioallantoid chick embryo membrane. The cerebrospinal fluid showed angiogenic activity in patients with primitive tumors of the central nervous system and also in cases where the tumor had extended into other organs. The cerebrospinal fluid of controls without tumor revealed angiogenic activity in 28% of the cases. There was a direct correlation between positive assays and age. Sixty‐two percent of the samples of ascites from cancer patients were positive. Only 25% of the controls were positive. Only 10% of the pleural fluid from cancer patients was negative, and 75% of the control samples were negative.