A preliminary communication published 4 years ago provided a brief overview of the chemical nature of the most important alkaloid of the Lobelia plant, Lobelin, and also reported a few things about one of the accompanying alkaloids, Lobelidine. The growing therapeutic importance of Lobelin, which is based on its respiratory stimulant effect, has made it possible, contrary to the fear expressed there, to continue the investigation. We have mainly concerned ourselves with two further crystallized alkaloids, Lobelanin and Lobelanidin, which were found in the scientific laboratory of the firm C. H. Boehringer Sohn Niederingelheim a. Rh. and which we were able to bring into a close relationship with Lobelin. The benefit of the work results thus also contributed to the constitution problem of the main alkaloid.