The infrared and radio continuum fluxes of 18 well-observed early-type stars are studied by comparing observations with theoretical models. The observations are taken from the literature. All available observations are included. The theoretical NLTE models for photosphere and stellar wind include free-free and free-bound emission as well as electron scattering. The good quality of the model is shown by the agreement of the theoretical and observed fluxes for most stars. For four stars (alpha Cam, delta Ori A, kappa Ori and zeta Pup) the observations suggest the presence of an additional emission mechanism (inhomogeneous and/or anisotropic outflow).