This document gives guidelines on the handling, storage, processing and documentation of venous whole blood specimens intended for the examination of human DNA isolated from circulating tumour cells (CTCs) during the pre-examination phase before a molecular examination is performed. This document is applicable to molecular in vitro diagnostic examinations performed and/or developed by medical laboratories, in vitro diagnostics developers and manufacturers, institutions and commercial organizations performing biomedical research. It is also intended to be used by laboratory customers including health institutions requesting examinations for their patients as well as biobanks and regulatory authorities. This document does not cover the isolation of genomic DNA directly from venous whole blood containing CTCs. This is covered in ISO 20186-2, Molecular in vitro diagnostic examinations - Specifications for pre-examination processes for venous whole blood - Part 2: Isolated genomic DNA. This document does not cover the isolation of specific white blood cells and subsequent isolation of genomic DNA therefrom. This document does not cover pre-analytical workflow requirements for viable CTC cryopreservation and culturing. NOTE 1 The requirements given in this document can also be applied to other circulating rare cells (e.g. fetal cells). NOTE 2 International, national or regional regulations or requirements can also apply to specific topics covered in this document.