The changes in thermal properties of maize starches during five stages of kernel maturity, (12, 18, 24, 30, and 36 days after pollination [DAP]), from three mutant genotypes, amylose extender (ae), sugary-2 (su₂), and waxy (wx) in an OH43 background, and the OH43 genotype were studied using differential scanning calorimetry (DSC). Within a genotype, DSC values of starches at 24, 30, and 36 DAP were similar to each other and often were significantly different (P < 0.05) from the values at 12 DAP, indicating possible differences in the fine structure of starch during endosperm development. For su₂ starches, the gelatinization onset temperature (T_oG) significantly decreased after 12 DAP and remained low throughout the study. The gelatinization range (R_G) had a similar pattern. For wx starches, T_oG at 18 DAP was significantly lower than at 12 DAP but tended to increase after 18 DAP. The R_G increased significantly after 12 DAP and significantly decreased after 30 DAP. Thus, thermal properties of starches during early development were different from those of their mature counterparts, and differences among the mutant genotypes and the normal starch originated from the earliest endosperm development stage studied (12 DAP).