OBJECTIVE: Near infrared spectroscopy (NIRS) uses light to monitor changes in the concentration of oxyhemoglobin and deoxyhemoglobin in living tissue non-invasively and in real time. Applications of NIRS in urology research and the strengths and limitations of this technology are reviewed. MATERIAL AND METHODS: A Medline and Pub-Med search using “spectroscopy” with heading terms: near infrared (NIR), near infrared spectroscopy (NIRS), urology, kidney, renal, urinary tract, bladder, prostate, testis and penis. RESULTS: Research incorporating NIRS has investigated a range of urologic conditions where a hemodynamic or vascular etiology is thought to be the underlying pathophysiology: as an aid to diagnosis in cryptorchidism, testicular torsion and vasculogenic erectile dysfunction; to evaluate renal metabolism and bladder dysfunction, and to study skeletal muscle metabolism in end stage renal disease. Strengths and limitations of NIRS relate primarily to the basic physics of how light in the NIR spectrum penetrates tissue and is scattered and absorbed. CONCLUSIONS: NIRS is a non-invasive, portable, real time measure of changes in tissue perfusion and oxygenation. In urology NIRS appears particularly applicable in ischemic conditions, and the evaluation of disorders associated with alterations in regional tissue hemodynamics (local changes in pressure, muscle contraction and urinary tract obstruction). Because the bladder detrusor can be interrogated transcutaneously NIRS may also provide a non-invasive means of evaluating patients with voiding dysfunction. Studies to date warrant further research and specific refinement of instrumentation and algorithm software for urologic applications, as NIRS could provide urologists with new methods of non-invasive physiologic diagnostic evaluation.