The flowers of tan, Fuligo septica (L.) Wiggers, form yellow slime masses (plasmodia), which are often to be found in woods after damp weather. For reproduction, the plasmodium transforms into a sessile flat crust (aethalium) which contains the blackish spore mass. Light plays an important role in the complex life cycle of the slime mold.[1] Consequently, attempts have already been made on several occasions to isolate substances from the plasmodia, for they could be potential photoreceptors. Thus, it was assumed that the yellow pigments were flavins, flavones, polyenes, pteridines or phenolic compounds.[3] In the following communication it will be shown that the yellow color of the plasmodia of Fuligo septica[4] is due to the occurrence of tetramic acids with a polyene chromophore.