Abstract: Objective To investigate effects of adenosine-3',5'-cyclic monophosphate (cAMP) on the degranulation of neutrophil stimulated by N-formyl-methionyl-leucyl-phenylalanine (fMLP).Methods Human neutrophil or polymorphonuclear leukocyte (PMN) isolation was performed by using the discontinuous saline-Percoll gradient technique. PMN degranulation was stimulated by fMLP and cAMP assayed by means of radioimmunoassay. myeloperoxidase (MPO) and lactoferrin (LF) were assayed by enzymology and indirect ELISA respectively.Results cAMP levels increased obviously following stimulation with fMLP for 1 and 5 minutes. The degranulation of neutrophil stimulated by fMLP was strengthened after pretreatment with cAMP-dependent PKA inhibitor h89 for 15 minutes.Conclusions The levels of cAMP increased obviously following stimulation with fMLP and neutrophil degranulation could be inhibited by fMLP itself.