Autosomal dominant polycystic kidney disease (ADPKD) represents a slowly progressing cystic kidney disorder which evolves into end-stage renal disease in the majority of patients. Currently, there are no established treatments to retard the progression of the disease, but several promising therapeutic options are being tested in ongoing clinical trials. An inherent dilemma for the investigation of therapies in ADPKD is the dissociation of the early onset and constant rate of cyst growth from the delayed but accelerated loss of renal function. In order to prevent the latter, one needs to act on the former, i.e. current belief by experts in the field is that (1) retardation of cyst growth will ultimately improve the loss of glomerular filtration rate, and (2) cyst volume is an ideal surrogate parameter for outcome in early ADPKD. The present review will discuss the utility and the techniques for kidney and cyst volume measurements to assess disease progression in ADPKD, and summarizes ongoing clinical trials testing novel therapeutic options.