The reemergence of colistin – an old class of cyclic polypeptide antibiotics into clinical practice as salvage therapy for the treatment of multidrug-resistant gram-negative bacteria is due to the lack of introduction of newer antibiotics and increasing resistance towards existing antibiotics. Colistin has bactericidal activity against gram-negative bacteria -P. aeruginosa, Acinetobacter baumannili, and klebsiella pneumoniae and Enterobacter species and well distributed in the liver, kidney, heart, and muscle whereas poorly distributed in the lung parenchyma, cerebrospinal fluid, bones, and pleural cavity. Since it is an older drug that was not much used, the knowledge of pharmacokinetic and pharmacodynamics properties are less. Except for the treatment of Cystic fibrosis, due to its serious nephrotoxicity and neurotoxicity, parenteral use was banned. Now according to recent studies their use parenterally for the treatment of ventilator-associated pneumonia, sepsis, meningitis and burn patients have shown less toxicity than earlier. This review focuses on colistin use in a critical care unit, resistance, susceptibility pattern, and toxicities.