cloud at $\sim$3 Mpc (Abadi & Edmunds 1978). HI 21 cm line emission was detected from this object, whereas in other cases it was not. However, in other cases far-infrared (FIR) emission was detected and could be identified (on morphological and positional criteria) with the obscuring clouds. FIR and HI emission were clearly detected in the case of the Okroy cloud (Wszolek 1988a, 1989). FIR emission was only marginally detected from the Rudnicki-Baranowska cloud (Wszolek 1988b). This indicates that the physical conditions in this kind of objects are far from being uniform. More such examples must be identified and their properties examined.

It is possible that the phenomenon of intergalactic hydrogen clouds could be related to the high-velocity cloud (HVC) complexes. These are HI structures whose radial velocities deviate by several 100 km s$^{-1}$ from the conventional galactic rotation. A recent review of HVCs is by Wakker & van Woerden (1997). Their Table 2 lists a few cloud complexes at distances $\geq$25 kpc; some of these may not belong at all to the MW. IRAS searches for FIR emission of HVC were negative (Wakker & Boulanger 1986), indicating that either the HVCs are dust-free or that their dust grains are 