Background and Purpose: The use of the holmium:YAG laser for treating benign prostatic hyperplasia has developed substantially over the last decade. We present our experience with holmium laser enucleation of the prostate (HoLEP) in critically ill patients. Patients and Methods: From January 1999 to May 2003, 40 critically ill patients with a mean age of 64.7 years (range 48-87 years) underwent HoLEP. Critically ill was defined as major comorbidity, including coronary and peripheral vascular disease, renal transplantation/immunosuppression, postradiation bleeding and sloughing, end-stage renal disease, advanced diabetes, severe anemia (hemoglobin <9.0 g/L), anticoagulant dependency, or bleeding diathesis. Preoperative and postoperative changes in hemoglobin (Hb) and sodium (Na), transfusion rates, and urethral catheter time were evaluated. This is a one-time instrument-insertion technique with the use of a large fiber and modification of the median lobe resection. Results: There were no significant changes in Hb (8.7 g/L to 8.5 g/L) or Na (135 mmol/L to 137 mmol/L). One patient was returned to the operating room for bleeding, and this and one other patient required postoperative blood transfusions. The urethral catheter was removed within 36 hours in 34 patients, and all patients were catheter free within 4 weeks of surgery. Conclusion: In our experience, HoLEP can be performed safely and effectively in patients who are critically ill.