Poly(ethylene terephthalate) bottles, commonly used for carbonated soft drink packaging, occasionally fail because of environmental stress cracking at the petaloid base. At raised temperatures, particularly during hot summer months, increased carbonation pressure of the contents aggravates susceptibility to stress cracking. In this study, numerical modeling with finite element analysis techniques was used to redesign the petaloid base of bottles to improve stress-crack resistance. An experimental design based on an algorithmic partial cubic method was employed. Mathematical modeling of the principal internal stress as a function of key design parameters identified optimal dimensions for the petaloid base. The improvement in stress-crack resistance was verified by experimental studies. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114:1126-1132, 2009