The use of recovery factors is a controversial issue among analytical chemists. The problem is most significant in the determination of pesticides or veterinary residues in complex matrices such as foodstuffs and in certain cases environmental materials e.g. soil). Typically, such methods of analysis rely on transferring the analyte from the complex matrix into a much simpler solution that is to be presented for instrumental determination. However, the transfer procedure results in losses of analyte. If an estimate of the true concentration is required (as it usually is – as it is usually compared to a statutory or contractual limit) compensation for these losses should be made in the calculation. There is no standardization between approaches to the use of recovery factors, an area which is becoming of increasing legislative importance. Many procedures universally regarded as valid practice when correctly executed involve compensation for analyte losses. The objective of this project is to bring together the different approaches and to make definitive recommendations as to the “best practice”. These would be in the form of a Protocol developed under the auspices of IUPAC and which would be adopted and used by various standardization organizations, governments and regulatory bodies.