The serum Ca levels in 100 patients with bronchogenic carcinoma were studied. Three patients without skeletal metastases displayed the full syndrome of acute Ca intoxication and had, respectively, serum Ca levels of 18, 17, and 17 mg/100ml. Eight patients had serum Ca levels higher than 12 mg/lOOml. Three patients without bony metastases had, respectively, serum levels of 18, 17, and 17 mg/100 ml, and suffered from acute Ca intoxication. Three other patients without bony metastases had serum levels of 13.8, 13.6, and 12.2 mg/100 ml, and were drowsy and hypotonic; 2 patients with bone metastases had serum Ca levels of 14.4 and 12.4 mg/100 ml; 1 had acute Ca intoxication and the other was drowsy and hypotonic. The association of hypercalcemia with bronchial carcinoma in the absence of skeletal metastases appears to be more common than supposed.