Description: Suitable methods for the determination of partial factors for use in limit state structural codes were investigated. The safety formats adopted in a number of national codes and draft codes are reviewed, with a commentary on some of the difficulties met at present in evaluating partial safety factors. Safety provisions currently used in the design of aircraft, ships and structures for nuclear energy plants are discussed. A study has been made of various constraints which should be considered in code drafting. These include requirements for human safety, economic considerations, legal obligations, insurance requirements and statutory control. It has been concluded that statistical reliability theory has been sufficiently developed to provide a basis for calculating probabilities of attaining a limit state. Present knowledge in this field is reviewed and a recommended Level II procedure is summarised. Examples are given of application of the method to a wide range of structural problems. To provide a basis for rationalising a new generation of codes, it is suggested that they be calibrated against valid experience or, more commonly, existing design rules. A calibration process is outlined which takes account of the various criteria which should be reflected in safety factors. Finally, the application of Level II reliability theory to the calculation of any chosen set of safety factors is explained and an example is given of the complete process of their evaluation. The recommendations arising from the study are summarised.