The occurrence of deformation in plastic bottles is a common problem in the bottling industry where bottles are blow molded, hot filled at high temperatures and sealed. Plastics have unique properties that make it difficult to predict when and why such changes may occur. The root cause of such deformation is unknown by many bottle producers and recent attempts have been made to minimize the occurrence of such defects. The purpose of this research is to determine which variables involved in the bottle production process influence bottle shape. Earlier variables that were tested included both blow molding resin and total bottle sidewall thickness. The result of changing these variables did not create a decrease in defects. The use of an Ishikawa fishbone diagram identified hot filling temperature a major variable that influences final bottle shape. This research summarizes the results of a series of tests that were developed to observe the effect of hot filling temperature on final bottle shape. A positive correlation between sidewall deflection and liquid hot filling temperature was observed. A series of tensile tests were also developed to analyze the strength of various regions of a blow molded bottle. An early Pareto Analysis determined that the parting line is more susceptible to defects than any other region of the bottle. This weakness was confirmed after the tensile tests proved that there is a statistically significant difference between measurements on the sidewall and parting line (pvalue < .001). The results of this thesis highlight the consequences of arbitrarily choosing a filling temperature with little understanding of the bottle's strength at high temperatures. Plastic bottle producers and hot filling companies should unite to determine the appropriate hot filling temperature before bottles are molded and filled.