Results: There were no serious adverse events or cardiovascular complications. Rosiglitazone was well tolerated by all patients, as judged by the Treatment Satisfaction Questionnaire for Medication. The PK studies indicated that the area under the curve was decreased by 40 to 50% and oral clearance of rosiglitazone was increased by 250 to 300% in patients with resistant FSGS compared with healthy controls and patients with nonproteinuric stage 2 chronic kidney disease.Conclusions: Rosiglitazone therapy was safe and well tolerated. PK assessment of potential novel therapies for resistant FSGS is necessary to define appropriate dosing regimens. There is rationale to evaluate the efficacy of rosiglitazone as an antifibrotic agent for resistant FSGS in Phase II/III clinical trials.