Anti-angiogenic agents targeting tumour vasculature have an established place in clinical practice, and new data are constantly emerging. However, despite rapid clinical uptake, a very large number of questions regarding these agents remain unanswered. One of the main hurdles in clinical practice is lack of accurate and feasible ways of assessing response to drug beyond tumour reduction on conventional imaging. This review summarises recent developments in the field of biomarkers of response to anti-VEGF drugs.