Fragments of the pituitary adenoma of a patient with Cushing's disease were maintained in defined culture medium. Immunoreactive (IR) ACTH, IR α-MSH, IR βlipotropin (β-LPH), IR β-endorphin, and IR γ-MSHs secretedfrom the adenoma were studied with gel permeation chromatography and the respective RIAs.The adenoma secreted roughly equimolar quantities of IR β-LPH plus IR β-endorphin, IR γ3-MSHs, and IR ACTHs. It also secreted IR α-MSH as well as IR γ1-MSH, although in a much lower concentration than the above four peptides. The secreted y3-MSH-like peptides were found to be glycosylated. The secretion pattern suggests that this particular adenoma processes the proopiomelanocortin molecule in pathways which encompass those of both the pars distalis and the parsintermedia.