The amorphous (a)-to-crystalline (c) phase transition has been studied in electron (e** minus ) and/or ion irradiated silicon (Si). The irradiations were performed in situ in the Argonne High Voltage Microscope-Tandem Facility. The irradiation of Si, at less than 10 K, with 1-MeV e** minus to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at less than 10 K, with 1. 0 or 1. 5-MeV Kr** plus ions induced the c-to-a transition by a fluence of approximately equals 0. 37 dpa. Alternatively a dual irradiation, at 10 K, with 1. 0-MeV e** minus and 1. 0 or 1. 5-MeV Kr** plus to a Kr** plus influence of 1. 5 dpa - where the ratio of the displacement rates for e** minus to ions was approximately equals 0. 5 - resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of radiation damage and the mobilities of point defects.