We report recent observational results of some ULXs collected with the 8.2m Subaru and with the ESO VLT telescopes. These observations have provided important information on the (inter-) stellar environments and have allowed to detect the optical counterparts of several ULXs. In two cases spectroscopic observations show stellar HeIIλ4686 optical emission reminiscent of X-ray heated accretion discs. This confirms the identification and provides independent evidence for an extremely high X-ray luminosity, thus excluding strong beaming effects. This opens the possibility to directly determine the masses of the binary component and to confirm or refute the existence of intermediate mass black holes (IMBHs).