The purpose of this experiment was to quantify the burn-down effect and chlorosis due to different times of herbicide glyphosate potassium 660 g l-1 application. The experiment was performed at Agriculture Faculty Research Station of Padjadjaran University, West Java Indonesia, from December 2015 to April 2016. The experiment was arranged in randomized block design with twenty treatments and each treatment was replicated two times. The treatments were application of herbicide glyphosate potassium 660 g l-1 at the dose of 2 L ha-1 on five transgenic corn varieties (C7 RR, 979 RR, 77 RR, 85 RR, and 95 RR) and five conventional corn varieties (C7, 979, 77, 85, and 95) at 15-day after planting and 20-day after planting. The result of this experiment shows that glyphosate potassium 660 g l-1 was effective to control weed in both transgenic and conventional corn varieties. The variety of transgenic corn exhibited smaller percentage of chlorosis (0-20%) and no burn-down effect following applications of glyphosate potassium 660 g l-1. On the other hand, chlorosis and burn-down effect were found in all conventional corn varieties. The yield of transgenic corn varieties was higher than the conventional corn varieties.