The set of aftershocks of the Erzincan (Turkey) earthquake of March 13, 1992 (MS=6.9) is shown to be multifractal, and characterized by a spectrum of generalized fractal dimensions Dq varying from D2=2.1 to D∞=1.35. It is shown that dimensions Dq decrease and then increase until coming back to there initial values few days before the large aftershock of April 20 (magnitude MS=4.6), for all values of q. Variation of fractal dimensions have yet been observed by other authors (Hirata and Imoto, 1991, Dongsheng et al., 1994, De Rubeis et al., 1993, Hirabayashi, 1992). ¿ American Geophysical Union 1996