Atmospheric models are presented for the outer layers of hot stars, O, of and Wolf-Rayet stars. The model is a two component hybrid model, consisting of a rapidly expanding component and a slower component. for the rapidly expanding component the energy sources are radiation pressure, a deposit of internally generated and stored energy, and radiation cooling. In this way a coronal layer with temperatures of the order of 4–7 million K is generated, with an extent of 1 to 2 stellar radii. The mass loss rates range between 10−6 and 10−4 Mo yr−1. The stellar wind velocity at infinity is of the order of 4000 km s−1. It is assumed that this rapid component interacts with the slow component, and gives rise to shocks. The corona as well as the shocks generated by the interaction of the two components can explain the observed X-rays.