Data from two cross-sectional studies carried out nine years apart and a nine-year follow-up have been analysed to clarify the relationship between height and ventilatory function. The regressions of FEV 0.75 and FVC on age and height are found to have a significant age-height interaction, and the longitudinal study demonstrates a correlation between height and both FEV decline and FVC decline. These two findings are shown to be equivalent, and both are found to interact with symptoms in that men with dyspnoes have larger age-height interactions and larger regression coefficients of FEV decline and FVC decline on height than men free of dyspnoea. Other published work is cited to support the results. It is shown that the findings can be explained on a model of proportionality, with both the FEV and the decline in FEV proportional to height. The data for the FVC fit the same model. Departures from this model which occur among the men with dyspnoes in the follow-up study are briefly discussed.