Unidirectional (UD) hybrid composite laminates based on glass fibers (GF) and high performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF) for 2 h. The total volume fraction of fibers of the hybrid composite was held constant and the proportion of PEF or GF was varied. The viscoelastic behavior of the hybrid composite was studied through dynamic mechanical analysis at different relative volume fractions of PEF. Parameters such as storage modulus (E′), loss modulus (E″), and loss factor or damping efficiency (tan δ) were determined in a resonant frequency mode. All the properties were compared between the hybrid composites. It was found that the glass transition temperature (Tg) increased to a higher region with the increase in relative volume of PEF. It was also observed that the efficiency of the hybrid composite increased with the increase in relative volume of PEF. © 1996 John Wiley & Sons, Inc.