Monitoring adolescent diets over time enables the assessment of the effectiveness of public health messages which are particularly important in vulnerable groups such as adolescents. In 2000, 424 children aged 11–12 years old completed two 3 d estimated dietary records. On the fourth day one nutritionist interviewed each child to clarify the information in the diary and foods were quantified with the aid of food models. Nutrient intake was calculated using computerised food tables. These children attended the same seven schools in the same Northumberland area as the 11- to 12-year-old children who recorded their diet using the same method in 1980 (n 405) and 1990 (n 379), respectively. Height and weight, and parental occupation were recorded in all three surveys for each child. Height and weight were used to calculate BMI, weight was used to estimate BMR and parental occupation was used to determine social class. Comparing the macronutrient intakes in 2000 with 1980 and 1990, energy intakes (EI) fell in boys (to 8·45 MJ) and girls (to 7·60 MJ). This fall may, at least in part, be due to an increase in low energy reporting. For 1980, 1990 and 2000 the percentage of boys with EI:BMR below 1·1 was 6, 15 and 23%, respectively; for girls, 3, 14 and 18%, respectively. Percentage energy from fat was unchanged between 1980 and 1990 but fell to 35% (about 76 g/d) in 2000, alongside a 3% increase in percentage energy from starch (30%). Percentage energy from non-milk extrinsic sugars remained above recommendations (16%; about 82 g/d). The number of overweight and obese children increased from 11% to 30% between 1980 and 2000. Positive changes have occurred in the Northumbrian adolescent diet but social inequalities, reported in previous surveys, remain.