Thin amorphous (&agr;) films of silicon created by ion implantation have been studiedinsituwhile undergoing the amorphous to crystalline transformation in the electron microscope. The specimens were prepared in such a manner that the amorphous/crystalline interface was viewed edge on and its advance during annealing was readily observed over distances of several microns. Growth rates and activation energies were measured. The active role that defects play during the regrowth process was also studied. An additional advantage of the technique was that in a single specimen different segments of the recrystallization front advanced along several different growth directions simultaneously, hence the effect of regrowth direction on the interface migration rate and defect formation was graphically displayed in a single specimen.