Adoption of SNOMED CT has not been as quick and easy as many people had hoped or expected. One reason is lack of education and hence understanding of what SNOMED CT does and how it works. We set out to answer the question "who needs to know what?" about SNOMED CT to help establish priorities for UK higher education. We devised an online questionnaire and obtained 177 responses, 51% health IT professionals, 42% clinicians. The sample was self-selecting of those with knowledge of SNOMED CT. The level of reported competence was greater among health IT professionals (33% rated themselves as competent) than among clinicians (5% rated themselves as competent) 92% of those who felt competent had received 3 or more days of training in SNOMED CT. This indicates the need for formal training in SNOMED CT. Most respondents indicated that health IT professionals ought to have a high level of competence in SNOMED CT, such that they are able to explain most if not all aspects of SNOMED CT to others. On the other hand, clinicians only require a fairly basic understanding.