A 43-year-old woman had diabetes insipidus and amenorrhea. There was panhypopituitarism on endocrine testing and visual field examination showed inexorably progressive loss to bitemporal hemianopsia. All radiographic findings were normal, but craniotomy disclosed the cause of this chiasmal syndrome to be an intrasellar abscess which, on culture, grew a Gram-positive anaerobe, Peptococcus. Intrasellar or pituitary abscess is rare, but it must always be considered in the differential diagnosis of the chiasmal syndrome, since loss of pituitary and visual function may occur much more rapidly than with the tumors most often responsible for this syndrome and since surgical cure is possible.