  Using numerical simulations and the Sheth-Tormen approximation we study the
mass function of dark matter halos in voids. We find that the void mass
function is significantly lower and its shape is different than that of the
field halos. We predict that in the standard LCDM model a void with radius 10
h^-1 Mpc should have 50 halos with circular velocity v_c > 50 km/s and 600
halos with v_c > 20 km/s.
