In this article we investigate the use of waiting time data as a performance indicator in health care in The Netherlands. We explain why the current publication of waiting time data fails to achieve one of the main goals: to have consumers and general practitioners act upon this information. The reason, we claim, is that even seemingly clear-cut, easily measurable and objective numbers such as waiting times need interpretation to become meaningful. Discussing four themes - the patient behind the number, the treatment behind the number, the strategy behind the number, and the specificity of the number - we will discuss just how deeply this need for interpretation affects the usability of 'waiting times' for purposes such as informing consumers. We will argue that this problem is due to not making a clear distinction between performance indicators for internal use and for external use. We conclude that the usefulness of the publication of waiting time data for consumers strongly increases when waiting times are guaranteed and related to treatment options like booking possibilities and other performance indicators such as patient satisfaction.