The semidiurnal baroclinic tides in the semi-enclosed basin which lies between the Greek Mainland and Peloponnesus were studied. The baroclinic wave field was found to be generated in the centre of the basin where bottom step topography exists. Typical amplitudes in a distance 8 km away from the generation region were found to be over 3 m during spring tides. Most of the energy could be accounted for by the first three vertical modes. During upwelling and down welling events which are frequent in this area during summer, the internal tide almost disappeared due to the destruction of the stratification.