Аннотация:The relative intensities of Balmer lines calculated on the basis of Sobolev's probability method (1947) and the observed decrements of T Tau stars in the catalog of Cohen and Kuhi (1979) are compared with spectral classes between K5 and M5. For the group of stars, G5-K5, studied by Grinin (1980), emission was found to be predominantly of an envelope type, with less of a part played by chromospheric radiation. In K5-M5 stars, however, the envelope makes a smaller contribution to the total radiation, and most of the emission arises in the dense gas at the surface of the star. A comparison of the Balmer decrements of T Tau stars of different spectral classes and flare stars shows that in a transition to stars of lower luminosity, the role of chromospheric radiation increases.