FDG PET is a promising technique for monitoring tumour response early during anticancer therapy. Progress, however, has been limited owing to the multitude of methods currently in use. Here, the most promising techniques for multi-centre trials are discussed briefly, with emphasis on the need for standardisation. In addition, an approach is presented for response monitoring studies using newly developed drugs. This approach makes use of a large database of response monitoring studies, which defines the relationship between simplified clinical methods and full quantitative analysis for classic cytotoxic drugs. For a new drug, first a pilot study is performed to assess whether it affects this relationship. Based on this pilot, it is decided whether or not a simplified clinical method can be used in further studies.