Objectives: To estimate the prevalence of tooth wear and to investigate factors associated with tooth wear in patients from general practices in the Northwest United States. Methods: Data on the diagnosis and treatment of oral diseases during the previous year were collected in a survey with a systematic random sample of patients (n = 1530) visiting general dentists from the Northwest Practice-based REsearch Collaborative in Evidence-based DENTistry (PRECEDENT) (n = 80). Prevalence ratios (PRs) of moderate to severe occlusal and incisal tooth wear by patient characteristics were estimated using cluster-adjusted multiple binomial regression for adults (18+ years) and children/adolescents (3-17 years). Results: For adults, the mean number of teeth with wear facets was 5.4 [95% confidence interval (CI) = 4.6-6.2] and 51% of the adults had four or more teeth with wear. Participants 45-64 and 65+ years old were 1.3 (95% CI = 1.1-1.6) and 1.4 (95% CI = 1.1-1.8) times as likely to have 4+ teeth with moderate to severe wear facets as participants 18-44 years old. Adult males had a 20% (PR = 1.2; 95% CI = 1.1-1.4) higher prevalence of wear than adult females. Adults who were using, or had ever used occlusal splints had higher prevalence of tooth wear compared to those who never used such appliances (PR = 1.3; 95% CI = 1.0-1.5). Adults with any periodontal bone loss also had a 20% higher prevalence of wear than adults without periodontal disease (PR = 1.2; 95% CI = 1.0-1.4). For children/adolescents, the mean number of teeth with moderate to severe wear facets was 1.6 (95% CI = 0.9-2.6) and 31% of the children had one or more teeth with wear facets. The adjusted prevalence ratio of tooth wear (1+ teeth with wear facets) for boys was 1.6 times as high (95% CI = 1.1-2.4) as compared with girls. The prevalence of wear for children 12+ years old was 50% (PR = 0.5; 95% CI = 0.3-0.8) lower than that of children <12 years old. Angle's class II was associated with higher tooth wear prevalence (PR = 1.8; 95% CI = 1.3-2.6) than class I. Children with posterior or anterior open bite had lower prevalence of wear than their counterparts (PR = 0.6; 95% CI = 0.3-1.0). No associations were observed between tooth wear and orthodontic treatment, missing teeth, and race/ethnicity. Conclusion: Tooth wear is a prevalent condition in this population. Among adults, higher prevalences of tooth wear were observed among those who were older, males, had used occlusal splints and had periodontal disease. Among children, higher prevalences were associated with younger age, male gender, class II malocclusion and the absence of open bite. Submitted on behalf of the Northwest PRECEDENT network, with support from NIDCR grants DE016750 and DE016752. © 2010 John Wiley & Sons A/S.