The predictive power of height for future ischaemic heart disease (IHD) was examined in 4860 men from two communities in South Wales and the West of England. At follow-up, men in the shortest fifth of the height distribution had experienced twice as many incident IHD events (fatal and non-fatal myocardial infarction) as was the case for men from the tallest fifth. Adjustment for age, social class and smoking habit failed to alter these relationships significantly. In the data from South Wales, determinants of height were examined; birth rank and number of siblings showed a trend with height. This trend was found only in men whose fathers were manual workers and may be related to inadequate nutrition in the higher birth ranks and larger families. These results support the suggestion that early childhood factors may be relevant to IHD in middle age and possible mechanisms are discussed.