Tropical tree height-diameter (<i>H:D</i>) relationships may vary by forest type and region making large-scale estimates of above-ground biomass subject to bias if they ignore these differences in stem allometry. We have therefore developed a new global tropical forest database consisting of 39 955 concurrent <i>H</i> and <i>D</i> measurements encompassing 283 sites in 22 tropical countries. Utilising this data...