In this article I argue that vagueness concerning consent to post-mortem organ donation causes considerable harm in several ways. First, the information provided to most people registering as organ donors is very vague in terms of what is actually involved in donation. Second, the vagueness regarding consent to donation increases the distress of families of patients who are potential organ donors, both during and following the discussion about donation. Third, vagueness also increases the chances that the patient's intention to donate will not be fulfilled due to the family's distress. Fourth, the consequent reduction in the number of donated organs leads to avoidable deaths and increased suffering among potential recipients, and distresses them and their families. There are three strategies which could be used to reduce the harmful effects of this vagueness. First, recategorizing the reasons (commonly referred to as ‘overrules’ under the current system) given by families who refuse donation from registered donors would bring greater clarity to donation discussions. Second, people who wish to donate their organs should be encouraged to discuss their wishes in detail with their families, and to consider recording their wishes in other ways. Finally, the consent system for organ donation could be made more detailed, ensuring both that more information is provided to potential donors and that they have more flexibility in how their intentions are indicated; this last strategy, however, could have the disadvantage of discouraging some potential donors from registering.