In this paper we discuss both theoretical and experimental results on the time dependence of the heat capacity of oriented Mn(12) magnetic clusters when a magnetic field is applied along their easy axis. Our calculations are based on the existence of two contributions. The first one is associated with the thermal populations of the 21 different S(z) levels in the two potential wells of the magnetic uniaxial anisotropy and the second one is related to the transitions between the S(z) levels. We compare our theoretical predictions with experimental data on the heat capacity for different resolution times at different fields and temperatures. [S0163-1829(99)01937-2].