This article aims to investigate the effects of five processing parameters and two geometric factors on replication quality of the microribs, as well as determination of the processing condition when different materials were used. Specifically, the considered parameters include barrel temperature, mold temperature, injection velocity, holding pressure, holding time, aspect ratio, and location of the microribs. The experiment results showed a considerable difference in replicated height of molded microribs with polymethylmethacrylate and polypropylene. Among the processing parameters, the barrel temperature and injection velocity significantly affected replication quality, whereas the holding pressure and holding time appeared to have little influence for both materials. The mold temperature was found to be a sensitive parameter only for polymethylmethacrylate. As for geometric factors, both aspect ratio and location of the microribs played important roles in achievable replication. In addition, simulation results showed good prediction on the trend of how process parameters affect replication, with a small amount of over prediction. POLYM. ENG. SCI., 50:2021–2030, 2010. © 2010 Society of Plastics Engineers