Interferences by uranium fission for95Zr,99Mo,103Ru,140La,141Ce and147Nd have been studied using a single comparator method with two monitors. The effect of the neutron energy spectrum on the interference factor was examined by using the effective activation cross section. All the activities of140La produced during neutron irradiation of uranium were included in the calculation of the factor for lanthanum. The calculated and experimental interference factors are in good agreement within 10% deviation. The results have been applied for the analysis of several rock samples containing uranium in a wide concentration range.