The central bank on the Italian flora and vegetation has been used to obtain information on the phytogeography of Sicily. The chorological spectrum of the Sicilian flora and the percentages of each phytogeographical category in 8 main environment-types have been analyzed by multivariate methods. The correlations between species with similar distribution patterns and environments are high. Species with similar ranges tend to have the same ecological behaviour. One of the main factors to which they respond is water availability in the soils.