The typical assumption is that patients with CKD will have progressive nephropathy. Methodological issues, such asmeasurement error and regression to the mean, havemade it difficult to document whether kidney function might improve in some patients. Here, we used data from 12 years of follow-up in the African American Study of Kidney Disease and Hypertension to determine whether some patients with CKD can experience a sustained improvement in GFR. We calculated estimated GFR (eGFR) based on serum creatinine measurements during both the trial and cohort phases. We defined clearly improved patients as those with positive eGFR slopes that we could not explain by random measurement variation under Bayesian mixed-effects models. Of 949 patients with at least three follow-up eGFR measurements, 31 (3.3%) demonstrated clearly positive eGFR slopes. The mean slope among these patients was +1.06 (0.12) ml/min per 1.73 m 2 per yr, compared with -2.45 (0.07) ml/min per 1.73 m 2 per yr among the remaining patients. During the trial phase, 24 (77%) of these 31 patients also had clearly positive slopes of 125I-iothalamate- measured GFR during the trial phase. Low levels of proteinuria at baseline and randomization to the lower BP goal (mean arterial pressure ≤92 mmHg) associated with improved eGFR. In conclusion, the extended follow-up from this study provides strong evidence that kidney function can improve in some patients with hypertensive CKD. Copyright © 2012 by the American Society of Nephrology.