  We consider the production of positrons in microquasars, i.e. X-ray binary
systems that exhibit jets frequently, but not continuously. We estimate the
production rate of positrons in microquasars, both by simple energy
considerations and in the framework of various proposed models. We then
evaluate the collective emissivity of the annihilation radiation produced by
Galactic microquasars and we find that it might constitute a substantial
contribution to the annihilation flux measured by INTEGRAL/SPI. We also discuss
the possible spatial distribution of Galactic microquasars, on the basis of the
(scarce) available data and the resulting morphology of the flux received on
Earth. Finally, we consider nearby 'misaligned' microquasars, with jets
occasionally hitting the atmosphere of the companion star; these would
represent interesting point sources, for which we determine the annihilation
flux and the corresponding light curve, as well as the line's spectral profile.
We discuss the possibility of detection of such point sources by future
instruments.
