Randomized clinical trials have failed to show benefit from increasing intensity of renal replacement therapy (RRT), but continue to be frequently utilized. In addition, intensive RRT is associated with an increase in adverse events potentially secondary to small solute losses, such as phosphate. We hypothesized that, compared to less intensive RRT, intensive RRT would lead to longer duration of mechanical ventilation.Does more-intensive renal replacement therapy in critically ill patients with AKI increase time to extubation from mechanical ventilation when compared with less-intensive therapy?The ATN study was a randomized multicenter trial of more-intensive (hemodialysis or sustained low-efficiency dialysis six times per week or continuous venovenous hemodiafiltration at 35 ml/kg per hour) versus less-intensive (hemodialysis or sustained low-efficiency dialysis three times per week or continuous venovenous hemodiafiltration at 20 ml/kg per hour) RRT in critically ill patients with AKI. Of 1124 patients, 907 who were supported by mechanical ventilation on study initiation were included in this cox-proportional hazards analysis. The primary outcome was the time to first successful extubation off mechanical ventilation.Patients randomized to more intensive RRT had a 33.3% lower hazard rate of successful extubation (HR 0.67, 95% CI 0.52 - 0.88, P<0.001) when compared to patients randomized to less-intensive RRT. Patients randomized to more-intensive RRT had on average 2.07 ventilator-free days, compared to 3.08 days in those randomized to less-intensive RRT (P<0.001) over 14 days from start of the study.Critically ill mechanically ventilated patients randomized to more intensive RRT have longer duration of mechanical ventilation compared to those randomized to less intensive RRT. The reasons for this, such as excessive phosphate loss from more intensive RRT, deserve further study to optimize the safety and effectiveness of CRRT delivery.