Light reflecting from a laser‐produced plasma was measured as a function of plasma density. Light pulses of a Nd‐glass laser (100‐psec duration and 1014−W/cm2intensity) were focused on a high‐pressure gas jet as a target. A distinct reflectivity maximum of 0.3 was observed for helium at a density value 30% below the critical density. The results are interpreted in terms of stimulated Brillouin scattering.