Theory of ac losses in the type II superconductors in the frame of the critical state model [J. Thompson, M. Maley, and J. R. Clem, J. Appl. Phys.50, 3531, 3518 (1979)] is applied to highTcmaterials (Y‐Ba‐Cu‐O) assuming an exponential drop of the critical current densityJcwith both magnetic field and temperature. The dependence of dc magnetic field (H1) at which ac loss minimum occurs on an amplitude of ac magnetic field (h0) and on temperatureTcis calculated numerically. The two maxima of the total ac losses are found: one of them is very close toTcand second maximum belowTcshifts to lower temperatures with increasing ac or dc magnetic field.