Wheat starch was autoclaved (121-degrees-C) for 1 hr in excess water. The subsequent formation of enzyme-resistant starch (RS) was studied as a function of time (at different incubation temperatures, i.e., 0, 68, and 100-degrees-C). The rate of formation and the maximum yields of RS (4, 6, and 10%, respectively) varied to a great extent. The relationship between incubation time, temperature, and the yields of RS was interpreted in terms of crystallization in an amorphous matrix, the starch gel being a partially crystalline polymer system. Upon incubation at 0-degrees-C, the nucleation rate was high and the propagation rate was low; the opposite was the case upon incubation at 100-degrees-C. At 68-degrees-C, an intermediate pattern was observed. Incubation of the autoclaved starch samples at two subsequent temperatures (0 and 68-degrees-C or 0 and 100-degrees-C)(two-step procedure) did not increase the RS yield significantly. X-ray diffraction showed qualitative differences among the crystallites formed at different temperatures. RS formed at 100-degrees-C (A pattern) was different from that formed by incubation at 0 or 68-degrees-C (B pattern). X-ray diffraction of RS formed in a process with two storage steps at different temperatures (0 and 68-degrees-C or 0 and 100-degrees-C), aiming at increasing yields by first favoring nucleation and then propagation, yielded B-type diffractograms.