The widespread lichen family Pyxinaceae has received less attention than other similarly widespread families, e.g. Parmeliaceae. Moreover, recent studies on the Pyxinaceae concentrate on the Old World tropics. The present study is based principally on material found in the Guianas, but during this study material from other neotropical regions has also been investigated, as well as much type-material. Based on this, this fascicle describes this family which is represented worldwide by ca. 15 genera with ca. 700 species, of which 8 genera with ca. 120 species occur in the neotropics, and 7 genera with 46 species are found in the Guianas.