A simple, sensitive, selective, and low-cost method is proposed for rapidly determining nitric oxide (NO) in some rat tissues. Polymer monolith microextraction (PMME) using a poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolithic column was combined with derivatization of NO using 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene (TMDABODIPY), and this was used to analyze the derivatives of NO by high-performance liquid chromatography (HPLC) with fluorescence detection at lambda (ex)/lambda (em) = 498/507 nm. The baseline separation of TMDABODIPY and its NO derivative is performed under simple conditions in which a C(18) column is used and eluted with 50 mmol L(-1) ethanolamine and methanol. The conditions for the extraction of NO derivatives were optimized. The limit of detection of NO was 2 x 10(-12) mol L(-1) (S/N = 3). The linearity range of the method was 9 x 10(-11)-4.5 x 10(-8) mol L(-1). The interday and intraday relative standard deviations were less than 5%. The proposed method was successfully applied to the determination of NO levels in some rat tissue samples including heart, kidney, and liver with recoveries varying from 87.1 to 95.2%.