Objectives: To compare annual rate of change in kidney function, as measured by estimated glomerular filtration rate (eGFR), in adult ADPKD patients treated with and without tolvaptan. Methods: From 20 May-19 to September 2022, 57 US nephrologists completed a web-based survey using medical records of ADPKD patients who were treated with tolvaptan for ?2 years (cases). A cohort of ADPKD patients in Mayo class 1C to 1E who were not treated with tolvaptan was obtained from CRISP, HALT-PKD and OVERTURE studies (controls). Cases and controls were matched 1:1 on baseline age, gender and chronic kidney disease (CKD) stage. Kidney function decline was compared between cases and controls using mixed models. Results: Of the 149 cases treated with tolvaptan, matched controls were identified for 110 cases. Among these 110 matched pairs, the majority were male (60%), aged 43 (SD: 10.1) years on average, and 76% were in CKD stage 3a or earlier. Mean eGFR at baseline was 60 mL/min/1.73m2 among cases and 63 mL/min/1.73m2 among controls. The annual change in eGFR was -2.23 mL/min/1.73m2 among cases vs -3.62 mL/min/1.73m2 among controls with a statistically significant difference of 1.40 mL/min/1.73m2 per year (95% CI: 0.05, 2.74, p =0.042). A second analysis, whereby cases and controls were matched on baseline age, gender and eGFR resulted in 98 matched pairs. In comparison of the 98 matched pairs tolvaptan was associated with a trend in reduction of decline rate by 1.18 mL/min/1.73m2 per year (95% CI: -0.22, 2.58, p =0.097). Conclusions: In the current analysis, tolvaptan showed real world effectivess in slowing decline in eGFR when compared to matched historic controls, consistent with its efficacy in clinical trials .