We present the clinical and histological findings of 11 cases of inflammatory anterior pituitary lesions, 8 of which were obtained during surgery and 3 of which were obtained from autopsies. Additionally, we extended the conventional classification of pituitary inflammatory disease by the new entity " secondary hypophysitis". Of the surgically obtained specimens 5 consisted of inflammatory extension into the pituitary gland out of the surrounding tissue. In all of these patients the inflammation originated from an additional tumor in the sellar region (4 craniopharyngiomas, 1 prolactinoma). These will be referred to as "secondary hypophysitis", an entity which has not yet been mentioned in the literature. Of the remaining 6 cases, 2 were granulomatous hypophysitis, 2 pituitary abscesses, 1 lymphocytic hypophysitis, and 1 showed extensive scarring of the anterior pituitary lobe due to preceeding lymphocytic hypophysitis. At histological examination the basic structure of the anterior pituitary was maintained in all cases. Relative counts of hormone-producing cells were normal. In secondary hypophysitis, the affected area was composed of fibrous tissue and granulation tissue. B and T lymphocytes were present in equal amounts. Granulomas were not found. Inflammatory infiltrates, granulation tissue and fibroses were seen in different proportions. Based on our results and three other cases reported in the literature so far, we think that the presently used classification of pituitary inflammatory diseases lacks an entity which describes a non-abscess-forming inflammation of the pituitary gland originating from an associated pathological process. Therefore, we introduced the term secondary hypophysitis to describe this fourth entity of pituitary inflammatory disease.