  Stable baryonic Q-balls, which appear in supersymmetric extensions of the
Standard Model, could form at the end of cosmological inflation from
fragmentation of the Affleck -- Dine condensate. We reconsider astrophysical
constraints on such Q-balls as dark matter candidates. Baryonic Q-balls
interact with matter by absorbing the baryon number and, effectively, leading
to a rapid baryon number non-conservation. We have recently shown that this
process can occur at a much faster rate than that used in previous
calculations. As a consequence, stability of neutron stars imposes a stringent
constraint on the types of Q-balls that can be dark matter. Only the Q-balls
that correspond to baryonic flat directions lifted by baryon-number violating
operators are allowed as dark-matter candidates.
