New product development (NPD) projects are characterised by task ambiguity, whereby the set of tasks necessary for project completion and the relationships between tasks are initially unknown and only emerge as the development process unfolds. This paper uses interview data from NPD project managers in a large telecom firm to examine the influence of product requirements ambiguity on NPD task structures. The findings are used to propose a taxonomy outlining four generic patterns by which NPD task structures change during the product development process as a result of requirements ambiguity-task expansion, contraction, substitution and combination. The results also highlight in general terms the role of communication, coordination, knowledge and problem solving as distributed NPD project teams struggle to resolve ambiguity. Knowledge of how NPD project task structures evolve can lead to improved strategies for managing projects with ambiguous requirements. Two general types of strategies are suggested, decomposition of project tasks to minimize interdependence between tasks and the flexible adaptation of NPD task structures as new forms of task interdependence are recognised during the development process.