It is hereby enlisted the underground fauna, both water and terrestrial of the Vigant -Pre Oreak system. Amongst the species found, only 6 out of 35 are troglobias. This fact is certainly connected to the fact that some of them are transported from the external waters and this also shows a remarkable vulnerability of the system. The Pre Oreak Cave is, moreover, the locus tyicus of Monolistra coeca julia. It is therefore important that these enviroments must be protected and kept far from economical interests in order to preserve, among the other things, their precious inhabitants.