Abstract: Numerous studies have investigated information systems development methodologies and practices over the past decade. However, relatively few have focused on the characteristics of project teams and how the project teams operate to create, configure, or assemble the systems under investigation. Furthermore, even fewer studies have considered the way in which analysts (modelers) create models to collaborate and share knowledge about requirements within the project teams. This situation is in stark contrast to the fact that the fundamental organizational unit used to conduct information systems development is the project team. This study used data gathered on how modelers working in project teams used grammars within a CASE (computer-aided systems engineering) tool environment to test a model based on ontological, task, individual, and contextual factors in an effort to explain the decision to use or not use a combination of grammars for modeling. The results found a strong association between recognition of ontological incompleteness in the grammars provided by the tool and the decision to use a combination of grammars. Moreover, the odds of a project team using grammars in combination are approximately 2 to 1, which is significantly reduced from the 5 to 1 odds of a similar occurrence reported for individual analysts (modelers) who did not work in project teams. Qualitative evidence highlighted the influence of corporate modeling standards and specialization on the use of sets of grammars within project teams. This result, in particular, is reinforced by recent findings by Kautz et al. (2007). An integrating mechanism (e.g., central model repository) was seen as highly significant in achieving high levels of consistency among the models generated by the project team. However, the influence of minimal ontological overlap among the grammar set used by the team was not seen as a significant influence on the decision to use combinations of grammars, although significant contextual factors may have confounded this outcome.