Wide-angle X-ray scattering (WAXS) and differential scanning calorimetry (d.s.c.) measurements were made on cellulose tributyrate (CTB). In one case, CTB precipitated from solution in powdered form was annealed at different temperatures. In a second case, CTB was isothermally crystallized either from the melt or from the glass. Samples annealed from the powder showed higher crystallinity with respect to samples crystallized from the glassy or molten state. By applying the Hoffman-Weeks method to the melting temperatures of isothermally crystallized samples, a value of 192 degrees C for the equilibrium melting temperature of CTB was obtained. From calorimetric results on samples with different crystalline/amorphous ratio, a linear dependence between Delta H-m and Delta C-p was found, whose extrapolation gave 34.5 J g(-1) for the equilibrium heat of fusion Delta H degrees(m). A correlation between the experimental melting enthalpy arising from d.s.c. measurements and the percentage crystallinity estimated by WAXS measurements was attempted. In this manner a second, surprisingly high, value (67 J g(-1)) for Delta H degrees(m) was found. The difference between the values obtained from the two methods is believed to be due to the presence of macroscopic order in the amorphous phase, which influences the value of the WAXS crystallinity.