Increasing specialisation and the growth of automated advice delivery systems are creating new problems in legal responsibility and ethical behaviour. Engineering and medical workers can expect early encounters !'ith these difficulties, which are essentially concerned with a new interpretation of 'due care' and of 'professional liability'. The precipitating factor in this debate is the emergence of usable 'expert' systems, which embody judgemental and operational knowledge, and are often designed to mimic the behaviour (if not the public pronouncements) of acknowledged experts in the field. The task of the knowledge engineer and of the professional worker using - or expecting others to to use - such automated advisory systems raises ethical problems both for individuals and for professional and learned societies. Sorne of these are considered in this paper with special reference to the arms length delivery of medical and nutrition advice.