Data from large prospectively collected ante- rior cruciate ligament (ACL) cohorts are being utilized to address clinical questions regarding ACL injury demo- graphics and outcomes of ACL reconstruction. These data are affected by patient and injury factors as well as surgical factors associated with the site of data collection. The aim of this article is to compare primary ACL reconstruction data from patient cohorts in the United States and Norway, demonstrating the similarities and differences between two large cohorts. Primary ACL reconstruction data from the Multicenter Orthopaedic Outcomes Network (MOON) in the United States and the Norwegian National Knee Lig- ament Registry (NKLR) were compared to identify simi- larities and differences in patient demographics, activity at injury, preoperative Knee injury and Osteoarthritis Out- come Score (KOOS), time to reconstruction, intraarticular pathology, and graft choice. Seven hundred and thirteen patients from the MOON cohort were compared with 4,928 patients from the NKLR. A higher percentage of males (NKLR 57%, MOON 52%; P \ 0.01) and increased patient age (NKLR 27 years, MOON 23 years; P \ 0.001) were noted in the NKLR population. The most common sports associated with injury in the MOON cohort were basketball (20%), soccer (17%), and American football (14%); while soccer (42%), handball (26%), and downhill skiing (10%) were most common in the NKLR. Median time to reconstruction was 2.4 (Interquartile range [IQR] 1.2–7.2) months in the MOON cohort and 7.9 (IQR 4.2– 17.8) months in the NKLR cohort (P \ 0.001). Both meniscal tears (MOON 65%, NKLR 48%; P \ 0.001) and articular cartilage defects (MOON 46%, NKLR 26%; P \ 0.001) were more common in the MOON cohort. Hamstring autografts (MOON 44%, NKLR 63%) and patellar tendon autografts (MOON 42%, NKLR 37%) were commonly utilized in both cohorts. Allografts were much more frequently utilized in the MOON cohort (MOON 13%, NKLR 0.04%; P \ 0.001). Significant diversity in patient, injury, and surgical factors exist among large prospective cohorts collected in different locations. Sur- geons should investigate and consider the characteristics of these cohorts when applying knowledge gleaned from these groups to their own patient populations.