There have been many exciting new breakthroughs in understanding tumour biology. This has opened up the possibility of personalized treatment for people with certain tumours. The epidermal growth factor receptor (EGFR) and K-ras are two such targets that can help classify tumours on a molecular basis and guide treatment decisions. However, there are still questions about how best to implement new molecular tests like these to characterize tumours in clinical practice. Potential obstacles include availability of good quality tissue specimens, access to the right test, and consensus about interpretation, funding, and availability. In this paper, we review these issues, by discussing these two examples in detail and suggest some actions for addressing potential barriers.