The initial step of any software engineering methodology is to form requirements. Recently, a goal-oriented approach to requirements has been proposed and argued to be beneficial. Goals also play a key role in the implementation of proactive software agents. However, although some agentoriented software engineering methodologies have incorporated (aspects of) goal-oriented requirements engineering, and although they target agent platforms that provide goals as an implementation construct, none of the methodologies provide a goal-oriented design process. We present modifi- cations to the Prometheus methodology which make it more goal-oriented in its design phases and report on an experimental evaluation comparing the effectiveness of the original and refined methodologies.