Many patients with metastatic carcinoma have an increase in urinary excretion of 17-hydroxycorticosteroids (17-OHCS), plasma concentrations of 17-OHCS, plasma total Cortisol, plasma nonprotein-bound Cortisol, or Cortisol production rate. A small portion of circulating Cortisol is excreted in the urine as unaltered or free Cortisol. This urinary free Cortisol, which is believed to reflect the average unbound plasma Cortisol circulating during the day, is an excellent measure of adrenal cortical function. In this study, we compared the urinary free Cortisol of 35 patients with metastatic cancer (10 small cell carcinomas of the lung, 8 other types of carcinoma of the lung, 8 breast carcinomas, and 9 miscellaneous carcinomas) with a group of 15 healthy age-matched volunteers. There were no significant changes in urinary free Cortisol excretion in the patients with cancer.