This is a 2 year, open label trial to evaluate the role of rapamycin as treatment for ADPKD. Patients will be randomized 2:1 to the rapamycin arm or to standard therapy. The dose of rapamycin will be adjusted so that patients obtain 24 trough levels of 4-6ng/ml. There will be a volumetric MRI measurement at the start and end of the treatment period. Patients will be monitored every 4 months throughout the study.