Work in this laboratory has demonstrated the ability of theophylline to stimulate the release of immunoreactive luteinizing hormone (IRLH) and follicle-stimulating hormone (IRFSH) in organ cultures of human foetal pituitary glands (Groom, Groom, Cooke & Boyns, 1971). Cyclic adenosine 3′,5′-monophosphate (cAMP), while enhancing IRFSH release, had only a minimal effect on the levels of IRLH secreted. The present study extends this work utilizing the organ culture technique and radioimmunoassay methods described previously (Groom et al. 1971). Theophylline, a phosphodiesterase inhibitor (Robison, Butcher & Sutherland, 1968), at a concentration of 10−2 mol/l caused equal stimulation of release of both IRLH and IRFSH from the pituitaries (Table 1). In contrast, 10−2m-cAMP, while stimulating the secretion of both IRLH and IRFSH, had a significantly greater effect on the latter (Table 1). The N6-2′-0-dibutyryl analogue of cAMP (dbcAMP) is more potent both in vivo and in vitro, probably