The aim was to identify potential predictors of ICU length of stay (LOS) for single lung transplant patients.Retrospective chart review.University medical center.All single lung transplant recipients for 1992 and 1993 at our institution.Data were collected from 69 patients. The median ICU LOS was 5 days, and this was highly correlated with the duration of mechanical ventilation. The mean acute physiology and chronic health evaluation (APACHE II) score was 10. Patients with pulmonary hypertension had the longest ICU LOS. Similarly, patients with a measured transpulmonary gradient of 20 mm Hg or less had a significantly shorter ICU LOS. Patients with an immediate postoperative PaO2/fraction of inspired oxygen (FIo2) ratio greater than 200 mm Hg and a flow mismatch between the two lungs of 30% or less also had a significantly shorter ICU LOS. Positive and negative predictive values for the immediate postoperative PaO2/FIo2 ratio of 200 mm Hg or less were 77% for an ICU LOS greater than 5 days, and the calculated receiver operating characteristic (ROC) curve area was 0.74.Overall, the immediate postoperative PaO2/FIo2 ratio of 200 mm Hg or less had the best positive and negative predictive values as well as the highest ROC curve area for predicting an ICU LOS greater than 5 days.