A Diophantine m-tuple is a set of positive integers such that the
product of any two distinct elements, increased by 1, is a perfect
square. We will derive an asymptotic formula which counts the number of
Diophantine quadruples with elements bounded by N by modifying the
Erdös-Turán inequality and a result of Hooley on the equidistribution
of solutions to polynomial congruences. This is joint work with Greg
Martin.