A short chronological review of cyanogenesis (Fig. 1) in vascular plants is given (Table 1). Subsequently the chemistry (Tables 2–4; Fig. 2) and biochemistry (Figs. 3–9) of cyanogenic plant constituents are summarized. Five biogenetical groups (A-E) of cyanogenetic compounds are presently known from vascular plants. The occurrence and function (Fig. 10) of cyanogenesis is sketched and causes of conflicting statements in phytochemical literature are briefly discussed. Finally the presently known distribution of the different pathways, and the resulting constituents, as well as of still unidentified cyanogenic compounds, is given. The paper ends with a short systematic appreciation of cyanogenesis as a systematic marker at higher categories. The differences between Pteridophyta, Gymnospermae and Angiospermae and the similarities between Liliopsida and the magnoliid and ranunculid part of Magnoliopsida are stressed and the uniformity of Passiflorales, including Flacourtiaceae as well as the heterogeneity of Rosaceae are outlined and discussed from the taxonomic point of view.