A survey of Portuguese financial corporations showed that their adoption of information technologies (IT) depends on strategic variables, such as competitive strategies, competitive aspects, business environment, and geographic strategies. The survey also revealed that firms adopting one information technology are likely to adopt others and that they follow a sequence in adopting information technologies. We identified the IT adoption sequence by estimating, through the Bayes theorem, the likelihood of a firm's adopting a specific technology after having adopted a set of more basic technologies. We propose a classification for information technologies according to their place in the adoption sequence: infrastructure technologies, intermediate technologies, and advanced technologies.