With the advent of one-stop prostate cancer diagnostic clinics, the findings of this study are of interest to readers who may be implementing MRI-US transrectal or transperineal fusion biopsies to their clinical practice. This prospective cohort study evaluated 779 consecutive MRI-US fusion biopsies performed by a single surgeon with no previous experience in fusion biopsies. Two parameters were used to define the learning process – efficiency (procedural time) and accuracy (clinically significant cancer detection rate defined as Gleason group ISUP Gleason group ≥ 2 for PI-RAD 3 lesions only). The end of the learning curve for efficacy was determined when there was <10% time difference for more than 90% of the following biopsies. The end of the learning curve for accuracy was determined when there was a <5% cancer detection difference for all consecutive biopsies. Procedure time decreased from 45 minutes in the first local anaesthetic transrectal fusion biopsy to 15 minutes after 109 biopsies before remaining stable. Time decreased from 55 minutes in the first general anaesthetic transperineal fusion biopsy to 18 minutes after 124 biopsies. Detection rates for PI-RADS 3 lesions remained stable at 50% after 104 biopsies for transrectal fusion biopsies and 55% after 119 cases for transperineal. The authors concluded that proficiency occurs after approximately 110 transrectal and 125 transperineal fusion-biopsies. Within the limitations of this study (definition of “end of learning curve”, biased learning curve for transperineal fusion, exclusion of analysis of PI-RADS 4 and 5 lesions due to small numbers), this study does add value to readers to highlight the provisions that departments need to consider prior to implementing their new service and the subsequent knock on effects for training junior trainees.