The 2200 m/sec neutron cross section for deuterium has been determined relative to that for 59Co by absolute counting of the 3H and 80Co produced by neutron irradiation. The result, expressed in terms of the 2200 m/sec cross section for 59Co in b, and of the tritium half-life in years, is (1.104 ± 0.014 × 10-3) [σ0(59Co)] [t1/2(3H)] mb. Assuming σ0(59Co) = 37.4 ± 0.3 b and t1/2(3H) = 12.262 ± 0.004 years, gives σ0 (D) = 0.506 ± 0.010 mb. The standard deviation of the mean value from 8 irradiations was ± 0.2%.