We report complex magnetic permeability or susceptibility measurements of three different laboratory-synthesised magnetic fluids. Microwave frequency range is used for the measurements. We used the reflection/transmission method in a coaxial line cell to obtain the complex permeability μ * . We have subjected the coaxial cell to a constant magnetic field applied parallel to the propagation direction. Nicholson-Ross equations are used to calculate the apparent permeability. Complex magnetic permeability is measured for three different magnetic fluids at microwave frequencies, at different DC-magnetic fields as well as temperatures. It is found that Mn-Zn and Mn-Zn-Gd samples show magnetic resonance behaviour while Mn-Fe sample shows both Neel relaxation and resonance phenomena in the DC applied magnetic field. The effective anisotropy constant and the anisotropy field measured on Mn-Fe fluid are much greater than the effective anisotropy constant and the anisotropy field measured on Mn-Zn and Mn-Zn-Gd fluids.