Background: Active surveillance (AS) is a safe and accepted option for managing men with low-risk prostate cancer. Nevertheless, some patients lack confidence in or access to AS. Focal therapy (FT) is a possible alternative to radical treatment for such patients. Objective: We evaluated dominant tumor (DT) progression across serial biopsies to determine whether men on AS could be reasonable candidates for FT. Design, setting, and participants: Men enrolled in AS at University of California, San Francisco between 1996 and 2017 with low/intermediate risk were included. Outcome measurements and statistical analysis: Changes in biopsy grade, volume, and focality of the DT over time were assessed. Focality (good or poor for FT) was defined by the number of cores, laterality, and contiguity of prostate sites containing tumor (based on pathology reports). Candidates (either for targeted/quadrant ablation or for hemigland ablation) were defined based on good focality, grade group (GG) 2, and low-volume disease. Patients were classified as favorable (GG 2 with good focality and concordant multiparametric magnetic resonance imaging [mpMRI]) or unfavorable (poor focality or high-volume disease or discordant mpMRI) for FT at surveillance biopsies. Results and limitations: A total of 1057 men met the inclusion criteria. The median number of biopsies per patient was three (interquartile range 2-4), and 196 patients (18.5%) underwent five or more biopsies. At confirmatory biopsy, 43% remained candidates for FT (67% for targeted/quadrant ablation and 33% for hemigland ablation) and 20% had a negative biopsy. Of the candidates for FT at initial biopsy, 11% had less favorable characteristics at confirmatory biopsy. Among candidates for FT based on both initial and confirmatory biopsies, 70% remained favorable for hemigland ablation at subsequent biopsies. Limitations include retrospective design and mpMRI information only at surveillance biopsy.