<jats:p> The structures of lucidine B, dihydrolycolucine, and lycolucine, representatives of a new type of Lycopodium alkaloid, have been determined, mainly on the basis of an X-ray crystallographic study of a derivative (N,O-di-p-bromobenzoyltetrahydrodeoxyoxolucidine B) of lucidine B. Dehydrogenation of lucidine B gives dihydrolycolucine which in turn has been prepared from lycolucine.