The experiment on Preliminary Yield Potential Comparison on ½ S d/3 and d/4 Tapping Systems of Some Hevea Clones in Cambodia was on farm research at Chup Rubber Research Station of Cambodian Rubber Research Institute (CRRI). The objective of the experiment was to investigate the preliminary yield potential comparison of the tapping system ½ S d/3 7d/7 and ½ S d/4 7dl7based on frequency of ethephon stimulation. The result for first year, revealed that clone IRCA 111 and PB 330 produced high yield in ½ S d/4 7d/7. ET 2.5%. Pa.4/y. Clone GT1 produced high yield ½ S d/3 7d/7. ET 2.5%. Pa.8/y. Clone IRCA 230 produced high yield in ½ S d/4 7d/7. ET 2.5%. Pa.12/y in Cambodian condition.