In this work new approaches to the design and implementation of clinical record systems are examined. Although information technology has long been successfully used in specific areas of medicine, very few situations exist where information systems are routinely used to support the medical record. The underlying thesis of this work is that the major reasons for this failure are the complexity and vastness of the medical field and the limitations of traditional methodologies and models for information systems development. I contend that there is need of an interdisciplinary basis for information systems development methodologies, which account for the multiple characteristics of medical care and for the related information systems. The research has been done from the perspective of a real hospital where the present goal of computerisation has seen the introduction of information systems in routine clinical practice. First, the problem of developing information systems for clinical laboratories is addressed, and a proposed, entity-based methodology developed and implemented. Then, a different entitybased approach is devised for the area of clinical records. This has been successfuly implemented in several clinical applications. However, due to limitations of this approach the natural language paradigm was selected as a basis for a different methodology. A multi-functional information model and system is devised, where information is represented and manipulated by means of different models and representations. These models correspond to three semiotic functions which clinical record systems should support. First, there is the Atomic Object Model which manipulates 'atomic' predications. This model is used primarily for the recording of simple facts (both knowledge and data). Second, there is the Medical Record Model which encompasses mostly structural and temporal properties of information and its major semiotic function is communication. It utilises abstraction principles such as 'generalisation' and 'aggregation'. The third model, the Clinical Model, is designed to incorporate different roles'that information can play in reasoning for clinical problem-solving. An information system was developed in which special care was given to problems of man-machine interaction, both in regard to information modelling and to manipulation of patient information. An integrated information system was developed gradually using different database management systems. A dozen different clinical applications have been developed and implemented and hundreds of physicians and nurses utilise the system in routine clinical work