Spectra of Comet Hyakutake were obtained with the International Ultraviolet Explorer (IUE) satellite on February 19, 1996, (20 days after its discovery on January 31), and later during its closest approach to the Earth at the end of March, with a geocentric distance of 0.1 AU. The cometary spectra are compared with a synthetic fluorescence spectrum of S2. On March 27, we find that both synthetic and cometary spectra are reasonably correlated. This suggests that S2 was probably present in the cometary spectrum with a production rate between 6.5¿1024 and 1.0¿1025 molec/s and an abundance of 0.005 to 0.009% relative to water. ¿ 1998 American Geophysical Union