Sixteen patients with a presumptive diagnosis of chromophobe adenoma of the pituitary were observed, without treatment. After varied intervals of up to 16 years, 13 were treated eventually. In 12, treatment was finally prompted by increase in size of the sella or by visual field defects. A cerebrospinal fluid rhinorrhea developed eventually in 1 patient in whom the adenoma had been allowed to destroy the sphenoid sinuses. Significantly greater residual visual field defects were present after treatment in 7 than when initially seen. Probably, some of these patients would have benefited by earlier therapy. Eighteen patients were retreated for recurrent chromophobe adenomas at intervals of from 1 to 17 years after either surgical decompression or combined surgical decompression and postoperative radiation therapy. The average interval was 3.5 years after surgical therapy and 8.9 years after combined treatment. Retreatment consisted of radiation therapy alone in 8 patients with improvement of visual fields in 4 and stabilized fields in 3. In 8 others, the combined retreatment by surgery and radiation therapy resulted in improvement in 6. No evidence of radiation injury was noted. The prognosis was much poorer in patients with lesions that invaded the parasellar tissues than in those with expanding but not locally invasive adenomas. Treatment in each patient was individualized and the relative efficacy of retreatment by radiation therapy alone or by combined treatment cannot be determined. It is the author’s opinion, however, that if the previous therapy was surgery alone, full course radiation therapy should be used for recurrence. If primary therapy had been both surgery and radiation therapy, retreatment should consist of surgical decompression probably followed by irradiation with dosage adjusted according to the initial dose and the interval. A primary irradiation failure should, of course, be treated surgically because of the likelihood of the adenoma being cystic.