Knowledge of clinical goals and the means to achieve them are either not represented in most current guideline representation systems or are encoded procedurally (e.g. as clinical algorithms, condition-action rules). There would be a number of major benefits if guideline enactment systems could reason explicitly about clinical objectives (e.g. whether a goal has been successfully achieved or not, whether it is consistent with prevailing conditions, or how the system should adapt to circumstances where a recommended action has failed to achieve the intended result). Our own guideline specification language, PROforma, includes a simple goal construct to address this need, but the interpretation is unsatisfactory in current enactment engines, and goals have yet to be included in the language semantics. This paper discusses some of the challenges involved in developing an explicit, declarative formalism for goals. As part of this, we report on a study we have undertaken which has identified over 200 goals in the routine management of breast cancer, and outline a tentative formal structure for this corpus.