In R v Morgan (1970), the Supreme Court of Victoria stated that for incapacity to consent to be proved, it must be shown that a person ‘has not sufficient knowledge or understanding to comprehend (a) that what is proposed to be done is the physical fact of penetration of her body by the male organ or, if that is not proved, (b) that the act of penetration proposed is one of sexual connexion as distinct from one of totally different character.’ It is my contention that this standard of knowledge is insufficient to allow a person to protect him/herself against the commonly recognized consequences of sexual acts, namely pregnancy and sexually transmitted diseases. Although the literature suggests that increasing the required standard of knowledge to encompass these facts would mean that many persons with mental impairment would be deemed incapable of consent, I argue that consent that is not based on a standard of knowledge sufficient to allow an individual to safeguard their own interests cannot be considered true consent. Law reform is required so that consent to sexual acts more closely resembles the informed consent required for medical treatment.