The use of electrochemical methods for the detection of various biological substances has provided real-time measurements giving insights into their roles in various physiological functions. The discovery that nitric oxide (NO) plays critical regulatory roles in a variety of physiological processes has prompted development of analytical techniques for the detection of this diatomic molecule in biological systems. This report will address the use of electrochemical techniques for the detection of NO. Several NO-sensitive electrodes have been fabricated and we present a discussion on the advantages and disadvantages of these techniques that will enable the reader to evaluate the best technique for a particular use. The fabrication of NO-sensitive devices for the electrochemical oxidation of solutions containing certain porphyrins (nickel tetra-N-methylpyridiniumporphyrin chloride, Ni(TMPP) and the corresponding apoporphyrin is described here. A key finding is that the lowering of the potential for oxidation of NO can be attributed to modification of the carbon surface and not the porphyrin film. The porphyrin does appear to improve the signal-to-noise ratio. An evaluation of various potential interferences will be discussed. Biological substances that potentially interfere with this type of electrode can be excluded by coating the electrode with Nafion membrane. A description of the coating procedure is presented and methods of distinguishing between NO and other substances such as nitrite, ascorbate, and catecholamines are discussed.