Using multistage cluster sampling, we conducted a household survey of diarrhoea among 4458 children under age 5 years in Dakahlia governorate from June 2002 to May 2003 to determine the prevalence and determinants of diarrhoeal diseases. Frequency of diarrhoea in the previous 2 weeks and last 24 hours were 23.6% and 8.7% respectively. Oral rehydration solution use rate was 24.3% among children with diarrhoea in the past 2 weeks. The frequency of diarrhoea was significantly higher among children in rural areas, those aged 6-24 months and of higher birth order, in the summer, when mothers were younger, had lower education or were not working, and when fathers had lower education or were farmers or manual labourers. Overcrowding, improper refuse disposal and non-flush toilets were also significantly correlated with diarrhoea incidence.