The bark structure and surface pattern of mature trees of Fagus sylvatica L., Quercus robur L. and Castanea sativa Mill, are described in detail and the rate of phloem growth calculated. Differences between Fagus and the other two species are ascribed largely to its slower phloem growth rate. Similarities between the bark of these Fagaceae and certain Dipterocarpaceae are described, and the significance of differences is explored. Comparison with other Fagaceae shows variation in bark in the family to be as wide as in Dipterocarpaceae. It is suggested that phloem growth rate is an important factor controlling bark surface pattern and has been important in bark evolution.