After defining the meaning of the term ‘smut fungus’, their current taxonomic classification is presented. There are to date, 1640 ‘true’ species of smut fungi that are classified into 2 phyla, 2 subphyla, 4 classes, 8 orders, 24 families and 90 genera. Recent changes to the classification of the smut fungi have produced some surprises when compared to their traditional classification. The variability of the symptoms produced by the smut fungi on their host plants, and the great morphological diversity of the spores is illustrated by selected pictures. Trends and perspectives in the research of the taxonomy of smut fungi are discussed. On the occasion of the imminent world monograph of smut fungi the necessity for urgent measures ensuring their global conservation is stressed. If present trends of habitat destruction continue, caused in large part by the human population explosion, many of the estimated 4000 to 4500 species of smut fungi become extinct before they are even discovered.