The method Used in the past 30 years for describing the swelling of polymers by solvents is mainly based on the Hansen three-dimensional solubility parameters. However, the subjectivity of its implementation as well as its limited success for several polymers, and in particular elastomers, which Constitute Choice materials for protective gloves, has been reported by several authors. In this article, data obtained by Zellers et al. with butyl rubber and a list of 53 solvents are analyzed to identify the parameters controlling the swelling of this elastomer. The absence of a global effect of the Hansen affinity, solvent molar volume and saturation vapor pressure, and Flory-Huggins interaction parameter has been confirmed. It was also shown that one of the main factors controlling the swelling of butyl rubber appears to be the chemical class of the solvents. Within these classes, a linear relationship between butyl rubber swelling and solvent saturation vapor pressure was observed, and the correlation with molar volume is almost as good. On the other side, no correlation can be obtained with the Hansen affinity. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3926-3933, 2008