Abstract: The mass loss rates of 53 early type stars, ranging in spectral type from O3 to B9 and in luminosity class from V to Ia(+), including Of stars, are used to investigate the dependence of the mass loss rates on the stellar parameters. The mass loss rates are based on observations of the radio flux, infrared excess, UV resonance lines, and H-alpha emission as found in the literature. These four sets of mass loss rates are compared with one another and corrected for systematic differences due to differences in the adopted velocity laws, by scaling them to the rates derived from the radio flux. Expressions are obtained which describe the mass loss rates or mass fluxes; the obtained relations agree neither with the present predictions for the radiation-driven wind theory nor with those for the fluctuation theory of mass loss.