Lychnin from the seeds of Lychnis chalcedonica and dianthin 30 from the leaves of Dianthus caryophyllus belong to the type 1 ribosome-inactivating proteins (RIPs). They have been crystallized by the vapour-diffusion method and the crystals diffracted to 1.7 and 1.3 A, respectively, using a synchrotron source. Lychnin and dianthin 30 crystals both belong to space group P2(1) with one protein chain in the asymmetric unit. The structure of dianthin 30 has been solved by molecular replacement using the coordinates of saporin-S6 as a model. The structure determination of lychnin, the sequence of which is not yet available, is in progress using the coordinates of other RIPs as models for molecular replacement.