Much legal and ethical attention in the area of eHealth focuses on the risks of health data processing ‘going wrong’ – a breach of privacy occurs, data is misused in an unauthorised way, or the analysis of data gives a faulty result. However, significant challenges are also posed by such processing where the data processing ‘goes to plan’ – the analysis gives the correct result in the way intended. Such challenges stem both from the nature of the information generated, and the new contexts in which this occurs. Thus, Big Data analysis may produce ever more information in relation to a person’s future health, usually of a probabilistic nature. In what situations should such information be returned to the subject (bearing in mind also that the decision-maker increasingly will be an entity outside the traditional health care context)? This chapter considers key ethical considerations that arise in such cases, and how well the law – through liability rules for harm, caused by failure to disclose, or by unjustified disclosure – is equipped to respond.