Background Greater knowledge regarding stool frequency and infrequency during pelvic and abdominal irradiation is needed to accurately identify patients at risk of either. Objective To describe occurrence of frequent and infrequent stools during pelvic-abdominal radiotherapy, and to compare quality of life (QoL) and activities of daily living (ADLs) of those patients experiencing frequent stools with those of patients experiencing infrequent stools. Methods Longitudinally during radiotherapy, 193 patients (64% had gynecological tumors) documented stool frequency, medications, and QoL using the Functional Assessment of Cancer Therapy-General. Results Fifty (26%) experienced frequent stools (>= 28 stools a week), and 17 (9%) experienced infrequent stools (<3 stools a week). The frequency of stools and the consumption of medication for diarrhea were highest the last week of the radiotherapy period (50% had >= 49 stools a week, and 50% could not even define the number of stools). Thirty-seven of the patients experiencing frequent stools used antidiarrhea medications. Patients with frequent stools experienced lower QoL (P = .035) and capacity in ADLs (P = .023) compared with patients not experiencing frequent stools. Conclusions A fourth of patients irradiated over pelvic or abdominal fields experienced frequent stools, defined as moderate to severe diarrhea, and those patients experienced lower QoL and capacity in ADLs compared with patients who did not experience frequent stools. Infrequent stools were rarely experienced. Implications for Practice Cancer nursing professionals should deliver evidence-based strategies to prevent frequent stools and treat frequent stools as an approach to lower the risk of impaired capacity in daily living and worsened QoL.