A retrospective case series study was performed in a 30-bed general intensive care unit (ICU) of a tertiary care hospital to assess the effectiveness and safety of colistin in 43 critically ill patients with ICU-acquired infections caused by multiresistant Gram-negative bacteria. Various ICU-acquired infections, mainly pneumonia and bacteraemia caused by multiresistant strains of Pseudomonas aeruginosa and/or Acinetobacter baumannii, were treated with colistin. Good clinical response (cure or improvement) was noted in 74.4% of patients. Deterioration of renal function occurred in 18.6% of patients during colistin therapy. Nephrotoxicity was elevated significantly in those patients with a history of renal failure (62.5%). All-cause mortality amounted to 27.9%. In this group of critically ill patients, an age of >50 years (OR, 5.4; 95% CI 1.3-24.9) and acute renal failure (OR, 8.2; 95% CI 2.9-23.8) were independent predictors of mortality. Colistin should be considered as a treatment option in critically ill patients with infection caused by multiresistant Gram-negative bacilli.