On the basis of 121 areas worldwide, the regressions of plant species-area relationships and of endemism-area relationships in log-log space are calculated. These formulae form the basis for calculating α-values. α-Values determine the ranking of biodiversity hotspots. In most cases, areas which have been published as biodiversity hotspots are characterized by high values of α, i.e. by rich compositions of vascular plant species and high rates of endemism.