  The observed 511 keV line from the Galactic Bulge is a real challenge for
theoretical astrophysics: despite a lot of suggested mechanisms, there is still
no convincing explanation and the origin of the annihilated positrons remains
unknown. Here we discuss the possibility that a population of slowly
evaporating primordial black holes with the mass around $10^{16}-10^{17}$ g
ejects (among other particles) low--energy positrons into the Galaxy. In
addition to positrons, we have also calculated the spectrum and number density
of photons and neutrinos produced by such black holes and found that the
photons are potentially observable in the near future, while the neutrino flux
is too weak and below the terrestrial and extra--terrestrial backgrounds.
Depending on their mass distribution, such black holes could make a small
fraction or the whole cosmological dark matter.
