Naphthalene contamination was observed in sterilized milk drinks contained in low-density polyethylene bottles. The determination of naphthalene in the packaging material by gas chromatography showed levels of naphthalene ranging from 0.7 to 2.0 µg g^–1. Analysis of the milk samples at the time of purchase by gas chromatography after extraction using a Dean and Stark apparatus showed levels of naphthalene in the range 0.01–0.03 µg ml^–1. The level of contamination in milk increased with storage time at room temperature (25 °C) and, depending on the concentration of naphthalene in the packaging material, values of 0.08–0.27 µg ml^–1 were found at the expiry date. Migration studies were carried out using peanut oil as a food simulant. The amount of naphthalene extracted by milk from the polyethylene at 25 °C over a period of 60 d was related to the amount that could be extracted using peanut oil at 66 °C for 30 h. A mathematical model was established to describe the observed migration of naphthalene into milk, and proved valid for calculating the level of naphthalene in milk using the optimum determined values of K and D_p.