OBJECTIVE: Colistin is a cationic polypeptide antibiotic with a cyclic structure that belongs to the polymyxin group. It was banned from clinical use because of its significant renal side effects, such as nephrotoxicity. However, the administration of colistin has recently been initiated again in the treatment of multi-drug resistant pathogens, such as Acinetobacter baumannii and Pseudomonas aeruginosa. Nephrotoxicity and neurotoxicity are the main problems encountered in the clinical use of polymyxins. The aim of this study was to determine the frequency and risk factors of colistin-related nephrotoxicity in the adult intensive care unit (ICU).