Background:Accurate assessment of tumor grade is critical for prostate cancer (PCa) Active Surveillance (AS). Multiple new technologies, including targeted biopsies and advanced imaging techniques like multiparametic magnetic resonance imaging (MRI) and high-resolution micro-ultrasound (microUS) may improve tumor risk stratification. Our preliminary data published in European Urology Open Science "Micro-ultrasound Versus Magnetic Resonance Imaging in Prostate Cancer Active Surveillance";showed similar clinically significant prostate;cancer detection between MRI and microUS in patients managed by active surveillance.;;Objective:To compare MRI and microUS for the detection of Gleason Grade Group ≥2 during AS. Methods:Prospective, paired diagnostic trial of 210 men with Gleason Grage Group 1 PCa managed by AS undergoing confirmatory biopsy between 12/2022 and 07/2023 at an academic tertiary care centre, with two other sites that will begin enrolling later this year. Patients included must be >18, be diagnosed with GG1 by any method,;being managed by active surveillance eligible for guideline recommended confirmatory biopsy.;To date, 72 men have been consented for the study and 40 have undergone their confirmatory biopsies with pathology results.;ClinicalTrials.gov Identifier: NCT05558241.;;Outcome Measurements and Statistical Analysis: The primary outcome is upgrading to Gleason Grade Group ≥2 stratified by PI-RADS and PRI-MUS scores. Statistical analyses will be performed using Chi square test, Fisher's exact test, and McNemar test. Results: Conclusions: [ABSTRACT FROM AUTHOR]