We study the asymptotic behavior of the ν-symmetric Riemman sums for functionals of a selfsimilar centered Gaussian process X with increment exponent 0 < α < 1. We prove that, under mild assumptions on the covariance of X, the law of the weak ν-symmetric Riemman sums converge in the Skorohod topology when α = (2ℓ + 1) −1 , where ℓ denotes the smallest positive integer satisfying 1 0 x 2j ν(dx) = (2j + 1) −1 for all j = 0, . . . , ℓ − 1. In the case α > (2ℓ + 1) −1 , we prove that the convergence holds in probability. * D.The previous convergence can be written as the following change of variables formula in law:f (X t ) = f (0) + t 0