On-farm testing of raw milk is expected to become of increasing importance in DHI-schemes in the future. Two scenarios of on-farm testing are identified. Conventional sampling and testing with on-farm milk analysers is compared to new in-line sensor scenarios. Both concepts provide some striking advantages when compared to traditional schemes, but open up new fields of concern about the quality of data. These must be thoroughly explored if data are to be used in DHI schemes. Especially on-line measurement of various parameters with automated sensors brings most interesting challenges for lowering the costs of generating data for DHI purposes and for speeding up the availability of data for herd management decisions. Of course the general principles of Analytical Quality Assurance (AQA) have to be fulfilled. In general, there should be a defined testing procedure and harmonized protocol when evaluating new methods to be used in DHI schemes. Key issues to be covered by this protocol are listed. Some more detailed thoughts about the evaluation of new analytical devices and the analytical quality control are mentioned. Obviously there is a need for the preparation and supply of suitable reference materials for on-farm, use. With such materials the calibration and control of on-farm devices is feasible. Education of the personnel handling the analytical systems is another crucial factor for the successful use of on-farm testing schemes. MTL WG of ICAR offers expertise and assistance to all interested groups to make the most of the opportunities lying ahead in the field of on-farm testing, thereby avoiding loss of analytical quality.