National audience ; INTRODUCTION: Optical spectroscopy refers to a group of novel technologies that uses interaction of light with tissues to analyze their structure and chemical composition. The objective of this article is to describe these technologies and detail their potential for assessing urological tumors. MATERIAL AND METHODS: It has been shown that optical spectroscopy can accurately analyse multiple solid tumors. Several publications specifically aimed at assessing prostate cancers, renal carcinomas and urothelial tumors. RESULTS: There are three types of spectroscopy that all use light focussed on a tissue and thereafter collect a specific reflected optical signal. Optical spectroscopy can differentiate benign (adenoma or inflammation) and malignant (adenocarcinoma) prostatic tissues. It can also distinguish normal bladder tissue from inflammatory or cancerous cells. Regarding renal tumors, spectroscopy can identify normal and tumoral tissue and differentiate benign and malignant tumors. Its diagnostic accuracy is about 85%. However, reported studies only concentrate on in vitro or ex vivo specimen and the numbers of patients are quite small. CONCLUSION: Optical spectroscopy can be envisioned as an "optical biopsy" tool. Potential applications in the clinical field are promising. Larger studies on in vivo specimen need to be undertaken to confirm phase I preliminary reports.