The effects of blow-molding process variables on the environmental stress crack resistance (ESCR) of high-density polyethylene (HDPE) bottles were studied. Experimental design was employed to test the effect of die temperature, mold temperature, molding time, and drop time. Bottles blown at each condition were tested using the internal pressure ESCR test. Through the use of regression analysis, the effect of each variable was quantified. Increasing die temperature, mold temperature, or molding time decreased ESCR. However, increasing drop time increased ESCR.