The agent-oriented approach has been successfully applied to the solution of complex problems in dynamic open environments. However, to extend its use to mainstream computing and industrial environments, appropriate software tools are needed. Arguably, software methodologies form the most important type of these software tools. Although several agent-oriented methodologies have been proposed to date, none of them is mature enough to be used in industrial environments. In particular, they typically don’t include catalogues of patterns that are necessary for addressing issues of reuse and speed of development. Two possible approaches to overcome such weaknesses in current agent-oriented methodologies are: to propose new methodologies, or to enhance existing ones. In this paper, the latter approach is taken, offering an enhancement of the Gaia methodology to include a catalogue, specifically concerned with a set of organisational patterns. Each of these patterns contains the description of a structure that can be used to model the organisation of agents in specific applications. The use of these patterns helps to reduce development time and promotes reusability of design models.