Slow and fast light with null amplification or loss of a light signal is experimentally demonstrated. This novel method for producing zero-gain slow and fast light takes advantage of the great flexibility of stimulated Brillouin scattering in optical fibers to generate synthesized gain spectra. Generation of optical delays and advancements with minor amplitude change is realized through the superposition of gain and loss profiles showing very different spectral widths, resulting in a synthesized spectral profile identical to an ideal electromagnetically-induced transparency. © 2006 Optical Society of America.