The environmental stress cracking (ESC) resistance of commercial virgin bottle and fiber grade poly(ethylene terephthalate) (PET) in contact with aqueous amine solutions was investigated. The ESC resistance, in terms of time to failure, was evaluated taking into account some factors, such as test temperature, molar volume (V-o) of the ESC agent, and molecular weight and degree of crystallinity (X-c) of PET. The specimens were tested in flexural mode using a constant load flexural creep test apparatus and also in tensile mode using a dynamometer. After the creep tests, the specimens were photographed with a digital camera and analyzed by scanning electron microscopy (SEM). It was found that ESC resistance was higher with the increase of ESC agent molar volume as well as with the increase of molecular weight and degree of crystallinity of PET. The highest temperature (60 degrees C) lowered the ESC resistance of the specimens, except for the crystalline specimens in n-butylamine that exhibited a higher ESC resistance at 60 degrees C, which can probably be attributed to the induced crystallization of the remaining amorphous phase by the plasticizing effect of n-butylamine.