The neutronic behavior of fusion reactor blankets is discussed, and transport-theory calculations are presented for two blanket designs. The areas investigated are (1) tritium breeding, (2) nuclear heating, and (3) neutron irradiation effects within the vacuum wall of the blanket, i.e., neutron-induced (a) atom displacements and (b) helium and hydrogen production. The two blanket designs considered consist of niobium as the vacuum wall and structural material, lithium or lithium in combination with lithium-beryllium fluoride (called“flibe”) as the coolant, and graphite as the neutron moderator and reflector. The results indicate that the tritium breeding potential of both designs is promising. The results also show that the tritium-breeding and nuclear heating characteristics of the lithium-flibe blanket are inferior to those of the lithium blanket. The calculated atom displacement rates and production rates of helium and hydrogen within the vacuum wall are essentially the same for both blanket designs.