This book has been written to cover the some important research related problems in reliability engineering .Book begins with introductory concepts of reliability, probability, availability, failure and repair rate, Mean time to system failure, system modeling, Byes theorem. Then further some research problems are discussed. Sensitivity analysis of urea fertilizer industry is also discussed. Further research problem of profit analysis of washing unit system is elaborated. Various important parameters in system modeling are also described e.g. transitional probability and mean sojourn time, path probability. Then problem of profit analysis is also discussed.