The present development of new therapies in oncology has been unlighted by the development of companion diagnostics.In general, 90% of drugs in the present therapeutic arsenal are only effective in 30-50% of patients treated.Identifying which patients may benefit and which not is becoming a very important question to answer for ethical, economical and therapeutically reasons.Since 2009, the development and increase of relevance in personalized medicine has underlined this problem.Today, it is necessary to present quite early, even at Phase Ⅰ stages, a Companion Diagnostic Device (CDD) that will be able to use the pharmacogenomic and pharmacogenetic identity of the patient to identify responders and non-responders, as also the potential incidence of adverse events based on the information available.The FDA with its recent Draft Guidance paper has initiated a new path into this area, influencing significantly the co-development of CDD and the product, and making even the approval of the product depending on the completed development of a CDD.Even if we are at early stages, already 114 recognized biomarkers have been approved by the FDA.The influence of this new trend is discussed in the paper and especially the role of the diagnostic laboratory,the present regulatory environment and the considerations when planning Phase Ⅰ studies in oncology within this framework.Technical and practical aspects for the performance of these trials are commented as well as the importance of the strategic planning.Finally, conclusions about the present environment and needs are listed as summary of the presentation.