  It has been recently suggested that stable, supersymmetric B-balls formed in
the early universe could not only be the dark matter at the present epoch, but
also be responsible for baryogenesis by their partial evaporation at high
temperatures. We reinvestigate the efficiency of B-ball baryogenesis and find
it to be limited by the diffusion of baryon number away from the B-balls.
Successful baryogenesis may only occur for B-balls with charges Q\simle 10^{20}
- 5\times 10^{23}, which is close to the observational lower limits on the Q of
a significant B-ball dark matter component. We also present some cosmological
constraints on the abundances of larger B-balls in the early universe.
