The molar heat capacities C-p,C-m of four crystalline compounds (5-aminouracil, 6-aminouracil, 6-amino-1-methyluracil, and 6-amino-1,3-dimethyluracil) were determined using a differential scanning calorimeter (SETARAM TG-DSC 111). The measurements were made at constant pressure between (298.15 and 343.15) K. Then the molar heat capacities were correlated with temperature. The contributions of C-CH3, N-CH3, and C-NH2 groups to the standard molar heat capacity values were evaluated. The experimentally determined C-p,m(o) values were compared with those calculated by the Chickos method.