This research investigated the extent to which a firm's internal and external environmental determinants influence the implementation of its HRIS. A conceptual framework that brought together the major factors thought to influence the firm's extent of implementing HRIS applications was developed. The key factors were presented under two broad dimensions: internal and external environmental factors. The data for this research were collected through structured-directed interviews with 236 respondents. The target respondents were business organisations in Jordan, and the key respondent approach was employed. The results show that 93% of the variance of the level of implementing HRIS applications could be explained by this combination, while the internal and external dimension could each explain only 90% and 62% of the variance of the level of implementing HRIS applications respectively. The research results indicate that the internal environmental dimension produces better explanation of the variation of the level of implementing HRIS applications than the external environmental dimension.