The lectin from the seeds of snake gourd (Trichosanthes anguina) has been crystallized in two forms using the hanging-drop method. Both the forms are hexagonal, with the asymmetric unit containing one subunit consisting of two polypeptide chains linked through disulfide bridges. Intensity data from one of the forms were collected at room temperature as well as at low temperature to 3 A resolution. Molecular-replacement studies indicate that the lectin is homologous to type II ribosome-inactivating proteins. Partial refinement confirms this conclusion.