Information analysis, a popular subject among vegetation ecologists not too many years ago, is revisited in this short monograph. The overview provided and the systematic presentation of ideas and algorithms should interest data analysts with backgrounds in this or other fields of natural science where the question of classifi- cation is addressed. The text gives the detailed descriptions and the listings of the computer programs. The authors were recipients of grant support from the Italian Consiglio Nazionale delle Ricerche "Gruppo Biologia Naturalistica" (E. Feoli) and the Canadian Na- tional Science and Engineering Research Council (L. Orl6ci) during completion of the project. The respective institutions of the University of Western Ontario and the University of Trieste provided facilities and computer time. Mrs. Stefani Tichbourne (London) typed the manuscript, Mr. Aulo Zampar (Trieste) gave computing assis- tance and Mr. Furio Poropat (Trieste) translated some programs. We are most grateful to them. E. Feoli M. Lagonegro L.