Reductions have played an important role in the evolution of lichens as in other groups of organisms. They are correlated with adaptations in changing ecological conditions. Several examples are discussed: Reduction of rhizines and rhizinomorphs, of the lower cortex, and of thalli in parasitical lichens. Furthermore, reductions of excipular structures in aspicilioid groups are described. Lecideine structure may also be seen as a reduction. Even paraphyses and apical apparati may be reduced in connection with changes of function. Reduction of spore number is widely spread in the system and seems to be similarly influenced by ecological factors. Complete loss of fruiting bodies in sorediate and leprarioid taxa should also be considered in this context