South Africa is a multilingual, multicultural context that poses communication challenges to health professionals. In a clinical trial, information must be thoroughly understood by participants in order for consent to be informed. Unfortunately, this is not always the case. This pilot study aimed to identify communication successes and breakdowns in informed consent sessions in an HIV vaccine trial. Two recorded consent sessions were analyzed using a hybrid sociolinguistic approach. Analysis revealed a lack of understanding and recall of information by participants, domination of sessions by the counselor, poor explanation of concepts, minimal participant contribution, and lack of validation of participant understanding. Interactions were not conducted in the participants' first language and a linguistically and culturally inappropriate consent document was used. It could not be said that consent was thoroughly informed in these cases. Investigating and adapting communication practices may prove valuable in ensuring truly informed consent and sound ethical practice.