Mold temperature is one of the most important factors regarding the quality and production rate in injection molding. Enhancing the performance of mold as heat exchanger is expecially critical to precision molding. In this study, mold temperatures measured at four selected points are used to assess the effects of cooling channel layout and core material on the cooling performance of injection molds for precision molding. Measured data indicate that mold temperature is a complex function of space and time (in-cycle and cycle-to-cycle). Three performance indices based on the measured data are first established for comparing the cooling performance between molds with various design parameters. They are the response to reach equilibrium, the thermal uniformity, and the average mold temperature. Molds implemented with three typical cooling channel configurations and inserted with three care materials are constructed. Their cooling performances during injection molding of disks with steps have been compared. Information from computer-aided simulation of the mold cooling process further facilitates the evaluation of mold cooling performance. General guidelines for planning of cooling channel layouts and selection of core materials are dawn from this study. Experimental and theoretical results suggest that high ther mal conductivity of the cores enhances the thermal uniformity, while high heat capacity retards the response of the system to reach thermal equilibrium. High convective area to mold volume improves the overall performance of mold as heat exchanger.