Aspects are behaviours that are tangled and scattered across a system. In requirements documentation, aspects manifest themselves as descriptions of behaviours that are intertwined, and woven throughout. Some aspects may be obvious, as specifications of typical crosscutting behaviour. Others may be more subtle, making them hard to identify. In either case, it is difficult to analyse requirements to locate all points in the system where aspects should be applied. These issues lead to problems achieving traceability of aspects throughout the development lifecycle. To identify aspects early in the software lifecycle, and establish sufficient traceability, developers need support for aspect identification and analysis in requirements documentation. To address this, we have devised the Theme approach for viewing the relationships between behaviours in a requirements document, identifying and isolating aspects in the requirements, and modelling those aspects using a design language. This paper describes the approach, and illustrates it with a case study and analysis.