INTRODUCTION The design safety assessment of safety critical systems has traditionally been carried out by comparing an illustrated description of the operation of the device with the specified design standard@ feature by feature and paragraph by paragraph. This method has worked well@ however@ it cannot be expected to remain reliable as the design of such systems and the related standards are becoming more complex. This increases the probability that some safety critical aspect of a design will be overlooked. Tools@ such as Fault Tree Analysis (FTA)@ help the study of operating faults in systems@ but there is no tool that can be used@ at the same time@ to help the study of system behaviour in the absence of faults. The approach described in this AOP attempts to do this. AIM The Aim of this AOP is to describe a procedure that may be used for the Integrated Design Analysis (IDA) of safety critical systems.