Kuh D (MRC National Survey of Health and Development, University College London and The Middlesex Hospital Medical School, Department of Community Medicine, 66–72 Gower Street, London WCIE 6EA, UK)and Wadsworth M. Parental height, childhood enivornment and subsequent adult height in a national birth cohort. International Journal of Epidemiology 1989, 18: 663–668. Low parental social class was associated with shorter adult stature in offspring in a national brith cohort, Since short adult stature is a risk factor for serious illness, particularly heart disease, origins of the observes class differences were sought in the childhood environment and in combined genetic and environmental factors represented by midparent height and birthweight. In addition to social class the childhood environmental factors of birth order, number of surviving younger siblings, overcrowding and mother's education were found to be significant and independent predictors of adult height, even after adjusting for parental heights and birthweight, and had therefore a long-term intragenerational effect. Both midparent height and birthweight constitute a combination of environmental and genetic influences, and therefore to some extent are an intergenerational effect. Improvements in environmental factors are thus likely to reduce social variation in adult height for both intra and intergenerational reasons.