Four patients with metastatic carcinoma to the pituitary gland are presented. Two of these patients had no previous history of malignancy and, based on clinical, laboratory, and radiological evaluation, a preoperative diagnosis of pituitary adenoma was made. In one patient, the histological diagnosis of two consecutive tumour specimens, obtained 1 year apart, was pituitary adenoma. The correct diagnosis of metastatic renal-cell carcinoma was not ascertained until autopsy. In the second patient, a diffusely infiltrating breast carcinoma was diagnosed by mammography and confirmed by biopsy, after pathological examination of the sellar tumour revealed carcinoma. The third patient underwent mastectomy 3 years earlier for breast carcinoma and had known metastatic disease. The fourth patient had known metastatic endometrial carcinoma when she became symptomatic from a pituitary metastasis. The incidence, clinical features, and pathophysiology of metastatic carcinoma to the pituitary gland are discussed.