The attained height and height growth rate of 9273 children participating in a longitudinal study of the health effects of air pollutants were analysed to assess the association between passive exposure to cigarette smoke and physical growth between 6 and 11 years of age. Children were measured annually for 2 to 6 years. Each height measurement was adjusted for sex and age by the NCHS anthropometric standards. Each child's adjusted heights were then re-expressed as level of attained height and growth rate. Attained height exhibited a dose-response relationship with amount of current maternal cigarette smoking (p less than 0.001). Children whose mothers smoked ten or more cigarettes daily were approximately 0.65 cm shorter than children of non-smokers, while children whose mothers smoked between 1 and 9 cigarettes per day were 0.45 cm shorter. However, passive smoking was not correlated with the child's growth rate. Exposure to paternal smoking was not significantly associated with height, either in terms of attained level or growth rate. These results indicate that passive smoking in the 6- to 11-year-old child does not continue to affect the growth rate of height and that the observed association between attained height and maternal smoking behaviour is due to exposures in utero and/or during infancy and the preschool years.