Although much work has been done on assessing safety requirements in programmable systems, one very important aspect, the integration of hazard evaluation procedures and requirements engineering, has been somewhat neglected. This thesis describes the derivation and application of a methodology, HAZAPS (HAZard Assessment in Programmable Systems). The methodology assists at the requirements stage in the development of safety-critical embedded systems. The objectives are to identify hazards in programmable systems, construct and model the associated safety requirements, and, finally, to assess these requirements. HAZAPS integrates safety engineering and software modelling techniques. The analysis of more than 300 computer related incidents provided the criteria used to identify, select and modify safety engineering techniques.