Children of the Nineties (ALSPAC) is a major longitudinal study of pregnancy and childhood. From its beginnings in 1990, it has had its own multidisciplinary ethics and law committee, with several interesting features. The committee is specific to this study and has a broad remit which has allowed it to be involved in planning the study as a whole, approving individual projects, and responding to ethical issues as they arise.

This article is the first of two covering the early work of the committee, the decision to establish a separate ethics committee and its initial role in formulating policies for ethical conduct in obtaining data from questionnaires, biological samples, and clinical and environmental tests. The intention is to offer readers the opportunity to consider theoretical questions of ethics in epidemiological research against the perspective of the real issues faced by one committee. By looking at the way in which this committee’s policies evolved, others may find useful strategies for dealing with similar dilemmas.