The financial performance of a farm is nowadays more dependent on the farmer's technical knowledge and management skills. To support management, microcumputer programs can be used.The Agricultural Economics Research Institute (LEI) developed the knowledge-based computer system GLOBAL-DETECTOR for globally analysing economical and technical bookkeeping-data and to give advice for improvement.This system, which software is programmed in the language muLISP, covers all returns and variable costs. For analysing the data, farm-adjusted standards arc used. The acquisition and presentation of knowledge for the diagnosis of performance is done by a method (IMAGINE) which is developed especially for this research.GLOBAL-DETECTOR supports decision-making. In this perspective, the extensive explanation-facilities possessed by the system arc crucial. First experiences with the system seem positive. Although farmer's individual whishes and demands cannot be fulfilled easily with computer systems, GLOBAL-DETECTOR may be used on a large scale on account of the flexibility and user-friendliness.