Ribosome-inactivating proteins (RIPs) from plants inactivate eukaryotic ribosomes, as far as studied by rendering their 60 S subunit unable to bind elongation factor 2. These proteins seem widely distributed and possibly ubiquitous in plants. They are either type 1, those consisting of a single polypeptide chain, or type 2 (ricin and related toxins), those consisting of two chains, one of which is a galactose-binding lectin. The literature on RIPs from 1982 has been reviewed with respect to the chemical and biological properties of RIPs, their use for the preparation of immunotoxins and new perspectives.