In 1965 I recorded the occurrence of two distinct forms of Myotis mystacinus in Central Europe; my preliminary ranking was that they were two subspecies, Myotis mystacinus mystacinus and Myotis mystacinus brandtii. Those findings were in agreement with previous information by Topál (1958) pointing out differences in the morphology of the baculum in Hungarian populations of that species, and even considering the differences between the two forms of specific value. The present paper is a summary of new discoveries concerning this problem; the characters distinguishing the two forms are discussed, whereas new information on their distribution in Central Europe is presented, and their systematic position is evaluated.