Weights and Heights of 22 349 children and adolescents aged 2 to 18 in Iran are reported. Data are from the 1990-1992 National Health Survey, a random cluster sample survey of 1 in 1000 families in all provinces of Iran. Multilevel models (Goldstein 1995) which take account of the survey design, reveal significant differences between provinces and between urban and rural children. Differences between urban and rural children, like differences between girls and boys, persist across all provinces and are certainly real. Differences between provinces may be partly due to differences in calibration. Charts based on the homogeneous subset of children living in urban Tehran may be used for all urban children, and in modified form, for all rural children. All the centiles of these charts are substantially below those of the NCHS charts, but the spread is similar so that there is no suggestion that the difference is due to the prevalence of gross malnutrition. The difference shows that the use of locally based growth charts are essential for assessing the growth of children in Iran.