For the purpose of obtaining load‐elongation curves, fused SiO2fibers a few &mgr;m in diameter, which were produced by Nichols’s method, were tested using the tensile‐testing machine which was specially prepared by Hiki and the author. Load‐elongation curves obtained showed nonlinearity which indicates that Young’s modulus becomes larger with increasing strain. Moreover, a distinct elastic hysteresis was observed in which increasing curves have different traces from decreasing ones and return to the origin smoothly. The nonlinearity of load‐elongation curves is explained as the macroscopic appearance of anharmonic interaction between atoms. On the other hand, an elastic hysteresis which has not been observed in metal whiskers is assumed to be caused by complex deformation of a random network of fused SiO2fibers.