If X is a random vector with n components we say that X is comonotonic if all it can be written as X = f(U) where f is a monotonous function from R to the n-dimensional space. Or, in terms of probability distributions, F is a comonotonic distribution if its support is carried by an increasing path in the n-dimensional space. It is obvious that if we have a selection of volume N from a comonotonic distribution, all the N points are on the graph of a monotonous curve. We intend to de ne an index of comonotonicity for any distribution F.