Objective. Chronic constipation is characterized by difficult, infrequent, or seemingly incomplete bowel movements. The Patient Assessment of Constipation Quality of Life (PACQOL) questionnaire was developed to address the need for a standardized, patient-reported outcomes measure to evaluate constipation over time. Material and methods. Items for the PAC-QOL were generated from the literature, clinical experts, and patients. Following principal components and multitrait analyses, 28 items were retained forming four subscales (worries and concerns, physical discomfort, psychosocial discomfort, and satisfaction) and an overall scale. Validation studies were conducted in the United States, Europe, Canada, and Australia, to evaluate the internal consistency reliability (Cronbach’s alpha), reproducibility (Intraclass Correlation Coefficients (ICCs)), validity (analysis of variance models), and responsiveness (effect size) of the PAC-QOL scales. Results. The PAC-QOL scales were internally consistent (Cronbach’s alpha >0.80) and reproducible (ICCs > 0.70, except for the satisfaction subscale ICC = 0.66). PAC-QOL scale scores were significantly associated with abdominal pain (p < 0.001) and constipation severity (p < 0.05). Effect sizes in patients reporting improvements in constipation over a 6-week period were moderate to large, with subscale effect sizes ranging from 0.76 to 3.41 and the overall scale effect size = 1.77. Similar findings were observed in validation studies conducted in Europe, Canada, and Australia. Conclusions. The PAC-QOL is a brief but comprehensive assessment of the burden of constipation on patients’ everyday functioning and well-being. Multinational studies demonstrate that the PAC-QOL is internally consistent, reproducible, valid, and responsive to improvements over time. Objective-Chronic constipation is characterized by difficult, infrequent, or seemingly incomplete bowel movements. The Patient Assessment of Constipation Quality of Life (PACQOL) questionnaire was developed to address the need for a standardized, patient-reported outcomes measure to evaluate constipation over time. Items and materials for the PAC-QOL were generated from the literature, clinical experts, and patients. Following principal components and multitrait analyzes, 28 items were retained forming four subscales (worries and concerns, physical discomfort, psychosocial discomfort, and satisfaction) and an overall scale. Validation studies were conducted in the United States, Europe, Canada, and Australia, to evaluate the internal consistency reliability (Cronbach’s alpha), reproducibility (Intraclass Correlation Coefficients (ICCs) and responsiveness (effect size) of the PAC-QOL scales. Results. The PAC-QOL scales were internally c PAC-QOL scale scores were significantly associated with abdominal pain (p <0.001) and constipation severity (p <0.05). Effect (Cronbach’s alpha 0.80) and reproducible (ICCs> 0.70 except for the satisfaction subscale ICC = 0.66) sizes in patients reporting improvements in constipation over a 6-week period were moderate to large, with subscale effect sizes ranging from 0.76 to 3.41 and the overall scale effect size = 1.77. Similar findings were observed in validation studies conducted in Europe, Canada, and Australia. Conclusions. The PAC-QOL is a brief but comprehensive assessment of the burden of constipation on patients’ everyday functioning and well-being. Multinational studies demonstrates that the the PAC-QOL is internally consistent, reproducible, valid, and responsive to improvements over time.