Large samples, \(\mathrm{ F^{n}( x,y ) }\)  is replaced by an asymptotic approximation for statistical decision of extremes. The discussions decide the fitness and accuracy of those approximations. The differentiable models, non-differentiable models of statistical decision, intrinsic estimation of the dependence functions, ready-to-wear model and estimations of the association between the margins with some examples are discussed in this chapter. Differentiable models, the logistic one gives a good fit but shows the logistic and the natural models can be very close and difficult to separate for moderate samples.