During last few years, a substantial (although circumstantial) evidence for the presence of the event horizons around some black hole candidates (BHCs) was accumulated. (1)X-ray Novae containing BHCs as compact components never produce Type I bursts. The most recent extensive observations failed to find even a single burst. At the same time, X-ray Novae containing neutron stars (NSs) produce frequently Type I bursts (as expected). (2) Quiescent (between the outbursts) luminosities of the systems containing BHCs are by about two and a half orders of magnitude dimmer than the systems containing NSs. As Chandra detects more and more sources in quiescence, this conclusion becomes stronger. BHCs are "blacker" because they have no solid surfaces on which part of the accretion energy could be released. (3) Systems containing BHCs and those containing NSs occupy different regions in the X-ray color-color diagrams. The difference might be naturally attributed to the fact, that the NS sources have solid surfaces and develop boundary layers in the process of accretion. (4) The inner part of the disc in some systems (GRS 1915+105) occasionally suddenly disappears. This implies that the matter is dumped on the compact object. However, we do not see the accompanying flash which should be produced if this matter hit the solid surface.
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