Background: Patient-reported outcomes (PRO) and electronic PRO (ePRO) play an important role in the development and approval of cancer products. Regulatory agencies are encouraging the inclusion of PRO-based endpoints that are indicative of clinical benefit in terms of patient symptoms and overall quality of life (QOL). Compliance with completion of ePRO assessments is an important component for obtaining accurate and high-quality data when conducting clinical trials. Traditionally, ePRO data in oncology trials has been collected mainly at clinic visits due to concerns over poor compliance at home. However, since symptoms and QOL can vary widely through a treatment course, it is often necessary to collect ePRO data more frequently in between clinic visits. It has been hypothesized that home completion, length of time in a study, and number of assessments may affect compliance. Methods: To address this hypothesis, ePRO compliance data was analyzed from two clinical studies in prostate cancer. Both studies used a handheld smartphone that contained an application to collect ePRO data. At the randomization visit, subjects completed ePRO assessments in clinic (2-3 questionnaires). Subsequently, all assessments were completed at home, including a daily diary and 1-4 questionnaires completed every 4-8 weeks for up to 14 months. Compliance was calculated as the number of assessments received divided by the number of assessments expected in a given assessment period. To evaluate assessment burden, each assessment period was categorized as requiring a lower number (daily diary and 1 questionnaire) or higher number (daily diary and 2-4 questionnaires) of assessments. Results: A total of 1,040 patients were included in the analysis. Overall compliance at the single clinic visit was 100%, which was expected since it was a required randomization visit. Overall compliance at home over 14 months was 80%. Compliance ranged from 78% to 89% over the duration of the studies, with no effect of time in the study on compliance. Compliance remained high even as patient numbers declined. Compliance when patients were required to complete a lower number of assessments (80%) was similar to compliance when patients were required to complete a higher number of assessments (79%). Compliance by region varied from 72% (Middle East) to 87% (Asia and Eastern Europe). Conclusions: The collection of ePRO at home provided high compliance that did not vary with length of time in the study or due to assessment burden. At home ePRO assessments provide an effective and feasible approach for recording symptoms and QOL in prostate cancer patients.