This article represents initial deliberation of an international task force appointed by the US National Multiple Sclerosis Society to develop recommendations for optimal clinical assessment tools for multiple sclerosis clinical trials. Presented within this article are the key issues identified by the task force during its initial year of deliberation. These include the precise purpose for a clinical assessment tool, the clinical dimensions to be measured in a multidimensional outcome measure, desirable attributes of an optimal clinical outcome measure, the complexities of multidimensional outcome measures, the relative merits of categorical clinical ratings and quantitative functional assessments, and a number of other important design issues that relate to the use of a multidimensional outcome measure. An action plan for analysis of existing data is summarized, as are the plans for more detailed recommendations from the task force.