Let {Xn : n ∈ Z d } be a weakly dependent stationary random field with maxima MA := sup{X i : i ∈ A} for finite A ⊂ Z d and Mn := sup{X i : 1 ≤ i ≤ n} for n ∈ N d . In a general setting we prove that P(M (N 1 (n),N 2 (n),...,N d (n)) ≤ vn) = exp(−n d P(X0 > vn, MA n ≤ vn)) + o(1) for some increasing sequence of sets An of size o(n d ), where (N1(n), N2(n), . . . , N d (n)) → (∞, ∞, . . . , ∞) and N1(n)N2(n) · · · N d (n) ∼ n d . The sets An are determined by a translation invariant total order on Z d . For a class of fields satisfying a local mixing condition, including m-dependent ones, the main theorem holds with a constant finite A replacing An. The above results lead to new formulas for the extremal index for random fields. The new method of calculating limiting probabilities for maxima is compared with some known results and applied to the moving maximum field.