OBJECTIVE To determine the prevalence of dental erosion in a stratified sample of 5-year-old children and to investigate whether demographic and dietary factors were associated. METHODS Cross sectional study in Cork City and County. METHODS A sample of 202 5-year-old children stratified on fluoridation status was selected. Measurement of erosion used a scoring system and criteria based on those used in the UK. Wear on the palatal and labial surfaces of primary maxillary teeth considered to be predominantly erosive was assessed. Demographic and dietary details were collected via a parental questionnaire. Statistical analysis was stepwise logistic regression. RESULTS In lifetime residents of fluoridated areas (n = 114) 47% had evidence of erosion; in 21% erosion had progressed to the dentine or pulp. The corresponding figures in non-fluoridated areas (n = 76) were 43% and 21% respectively. The variables significantly associated with erosion to dentine or pulp were low socio-economic status, measured by low family income and the frequency of fruit squash and carbonated drink consumption. CONCLUSIONS The prevalence of dental erosion overall was 47%, in 21% erosion affected the dentine or pulp. Levels in fluoridated and non-fluoridated areas were similar. Low socio-economic status and frequency of fruit squash and carbonated drink consumption were associated with erosion extending to dentine or pulp.