With the general trends of the international development of codes, specifications and recommendations for a fire engineering designs a background, the rapidly expanding modelling capabilities are demonstrated and exemplified with respect to the fire growth in a compartment, the fully developed compartment fire, the reaction to fire of materials, the fire spread between buildings, and the fire behaviour of building structures. The progress within the field of fire research and design is now characterized by a real breakthrough towards an increasing application of analytical methods with an improved connection to real fire conditions and based on well defined functional requirements and performance criteria.