The effective resonance integral of uranium carbide rods has been measured, as a function of the surface-to-mass ratio, in the range 0.09 < S/M(cm2/g) < 0.3. The experimental technique used was based on the comparison of 238U resonance neutron-capture induced activities of UC rods of varying diameter and of a U reference rod, irradiated in a slowing-down neutron flux. This technique avoided the need for the determination of a correction factor to the data, taking into account the slight departure of the neutron spectrum from the ideal 1/E dependence. The neutron slowing-down flux has been monitored by activation of Au and Mo detectors. The results of the experiment are summarized by the following expression: RIUC = 3.14 + 26.95 (S/M)1/2 ± 4.5%b. Dresner's equivalence theorem has been used to relate the above results to the effective resonance integrals measured for U and UO2. The equivalence parameters resulting from the original treatment and from the modified treatment proposed by Levine were both applied. The close equivalence which was found for the measured resonance absorption by U, UO2, and UC when using the latter parameter, gave an indirect support to the validity of Levine's calculation model.