This paper examines the problem of structural response in a multiple load blast environment. Due to the non-deterministic nature of the problem, the method considers the failure probability of the structure after each blast. The structure is modeled as a single degree of freedom system with a resistance function which provides for an approximate degradation in strength. The method considers uncertainties in both structural and blast load parameters. Load and resistance are assumed to be lognormally distributed. A failure probability is computed after each blast.