The results of microwave resonance measurements of thegfactor and the first- and second-order anisotropy fieldsK1/MandK2/Mare summarized for crystals with the nominal compositionCoxMn1−xFe2O4, where0 ≤ x ≤ 0.10. In the region150°K<T<300°K &Dgr;(K1/M) = Ax,&Dgr;(K2/M) = −Bxandg = a+bx.&Dgr;(K1/M)is the cobalt contribution toK1/M; similarly for&Dgr;(K2/M). The results forK1/Mare in agreement with publishedvalues determined statically on the same crystals. ForT = 290°K, 260°K, 230°K, 200°K, 170°K, and 140°K,Bis 510,1790, 4600, 10 300, 22 400, and 50 000, respectively. At 260°K thevalues foraandbare 2.003 and 0.41 respectively, at 9400 Mc;at 17 000 Mc the values are 1.992 and 0.42. For the lower frequencyat 170°K the values are 2.004 and 0.64. The two microwavefrequencies were used only above 77°K; in this range thegvalues are isotropic to better than 0.5%. At 4.2°K the effect ofthe cobalt upon the variation of resonance field with direction in a(110) plane cannot be accurately described byK1/MandK2/M.The results are compared with the successful theory for the cobaltion substituted intoFe3O4. It appears that modification of theoriginal model is necessary to take into account the differingenvironment of the cobalt ion when substituted intoMnFe2O4.