One hundred and forty 'normal' children aged 0-5 years, selected from three large general medical practices to represent a wide socioeconomic range, were seen monthly for periods of at least one year. Average growth patterns, previously shown to be related to the energy value of diets, conformed to British standards. Height and weight were not significantly related to socioeconomic status, maternal 'efficiency', number of sibs nor place in family. About half the children aged 0-5 years or less changed growth 'channels', falling to 0-4% in children aged 2 years or more. Respiratory illnesses showed seasonal changes, but growth rates did not, and there was no evidence that illness of any kind or severity had more than a transient effect on growth rates. Developmental test scores were not found to be related to growth rates. Girls tended to have higher scores than boys. Children from non-manual families and those with sibs at least 5 years older scored more highly in tests of language than those in other types of family.