The microstructure and magnetic properties of Li0.5-x/2 COx Fe2.5-x/2 O-4 (where x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7) ferrites have been reported. The ferrite samples were prepared by standard double sintering ceramic technique and structural analysis was carried out using X-ray diffraction. The lattice parameter (a) increases with increase in x. The average grain size obtained from SEM micrographs shows an initial decrease up to x=0.4 and then it increases. The saturation magnetization (M-s) and initial permeability (mu(i)) decrease with cobalt content up to x=0.4 and then a small increase is observed in case of mu(i). This has been attributed to high positive value of anisotropy constant (k(1)) for Co2+. The Curie temperature of the samples decreases with increase in the content of cobalt (x) due to reduction in the A-B interaction. The initial permeability of the samples remains almost independent of frequency in the frequency range studied viz. 1 kHz to 1 MHz. The measurement of AC susceptibility with temperature reveals the single domain (SD) state of the samples.