Using the machinery of zonal polynomials, we examine the limiting beha
vior of random symmetric matrices invariant under conjugation by ortho
gonal matrices as the dimension tends to infinity. In particular, we g
ive sufficient conditions for the distribution of a fixed submatrix to
tend to a normal distribution. We also consider the problem of when t
he sequence of partial sums of the diagonal elements tends to a Browni
an motion. Using these results, we show that if O-n is a uniform rando
m n x n orthogonal matrix, then for any fixed k > 0, the sequence of p
artial sums of the diagonal of O-n(k) tends to a Brownian motion as n
--> infinity.