Background Oral disease is a potentially treatable determinant of mortality and quality of life. No comprehensive multinational study to quantify oral disease burden and to identify candidate preventative strategies has been performed in the dialysis setting. Methods The ORAL disease in hemoDialysis (ORALD) study was a prospective study in adults treated with hemodialysis in Europe (France, Hungary, Italy, Poland, Portugal and Spain) and Argentina. Oral disease was assessed using standardized WHO methods. Participants self-reported oral health practices and symptoms. Sociodemographic and clinical factors associated with oral diseases were determined and assessed within nation states. Results Of 4726 eligible adults, 4205 (88.9%) participated. Overall, 20.6% were edentulous [95% confidence interval (CI), 19.4-21.8]. Participants had on average 22 (95% CI 21.7-22.2) decayed, missing or filled teeth, while moderate to severe periodontitis affected 40.6% (95% CI 38.9-42.3). Oral disease patterns varied markedly across countries, independent of participant demographics, comorbidity and health practices. Participants in Spain, Poland, Italy and Hungary had the highest mean adjusted odds of edentulousness (2.31, 1.90, 1.90 and 1.54, respectively), while those in Poland, Hungary, Spain and Argentina had the highest odds of ≥14 decayed, missing or filled teeth (23.2, 12.5, 8.14 and 5.23, respectively). Compared with Argentina, adjusted odds ratios for periodontitis were 58.8, 58.3, 27.7, 12.1 and 6.30 for Portugal, Italy, Hungary, France and Poland, respectively. National levels of tobacco consumption, diabetes and child poverty were associated with edentulousness within countries. Conclusions Oral disease in adults on hemodialysis is very common, frequently severe and highly variable among countries, with much of the variability unexplained by participant characteristics or healthcare. Given the national variation and high burden of disease, strategies to improve oral health in hemodialysis patients will require implementation at a country level rather than at the level of individuals.