Valid consent requires the potential research participant understands the information provided. We examined current practice in 50 proposed Clinical Trials of Investigational Medicinal Products to determine how this understanding is checked. The majority of the proposals (n = 44) indicated confirmation of understanding would take place during an interactive conversation between the researcher and potential participant, containing questions to assess and establish understanding. Yet up until now, research design and review have not focussed upon this, concentrating more on written material. We propose ways this interactive conversation can be documented, and the process of checking understanding improved.