This article focuses on three scenarios in which residual biological materials are turned into research collections during the procedure of procuring these materials for diagnostic, therapeutic or other non-research purposes. These three scenarios differ from each other primarily because they employ different models of consent: (a) precautionary consent, which may be secured during the collecting procedure; (b) the presumed consent model, which may be applied during the collection of materials; and (c) consent for research use of identifiable human biological materials, which may be skipped entirely. These scenarios offer additional sources of biological samples for research purposes and at the same time seem to offer even more flexibility in terms of stringency of consent as compared with the more traditional models of broad consent in prospective research collections and the waiver of consent in retrospective research. Our discussion leads us to think that precautionary consent is preferable to presumed consent and no consent when handling issues of consent in the use of residual human biological materials for research. However, such precautionary consent should not be construed as blanket, unrestricted consent for any future use.