The diagnostic usefulness of the epinephrine provocative test was assessed in three patients with functioning metastatic carcinoid tumors at a time when they had experienced no spontaneous flush reactions. One of these patients later developed severe flush reactions; the other two, who were followed until the time of their deaths, never flushed. The presence or absence of flushing was not related to the levels of serotonin in the blood or 5-hydroxyindoleacetic acid in the urine. The epinephrine provocative test was positive in the patient who later developed spontaneous flushes and negative in the other two. This finding indicates that the failure to induce a flush with the epinephrine provocative test does not exclude the diagnosis of a functioning carcinoid tumor in patients without spontaneous flushes.