We review conditions for the preservation of the FKG (Fortuin-Kasteley
n-Ginibre) inequalities in cellular automata and coupled map lattices.
In addition, conditions are derived on the transition probabilities f
or N-state probabilistic cellular automata which insure monotonicity a
nd preservation of FKG inequalities. This can be used, for example, to
prove normal fluctuation and large deviations theorems for these syst
ems. A number of examples of probabilistic cellular automata and coupl
ed map lattices that preserve positive correlations are presented and
the implications of FKG inequalities are discussed.