In evaluating the reliability of a system with redundant components, it is often assumed that the components are independent. However, this assumption is rarely valid in practice. In this thesis we survey the effect of adding redundancy on the reliability and it`s measures when components are dependent. A number of bivariate distributions that can be used the modeling of dependent components are compared. The results are then compared with the case of independent components Accordingly the results would be useful in reliability analysis as well as for designer who are required to take in to account the possible dependence among the components.