The ABR sessions in an ATM network share the bandwidth left over after guaranteeing service to CBR and VBR traffic. Hence the bandwidth available to ABR sessions is randomly varying. This bandwidth must be sharedby the sessions in a max-mn fair fashion. Our point of departure in this paper is to formulatethe problem of determining the max-min far session rates as the problem of finding the root of a certain nonlinear vectorequation;the same formulation alsoarises with our notion of maxmin famess with positive MCRs. This formulation allows us to use a stochastic approximation algorithm for online distnbuted computation of the max-min fair rates We use the well known ordinary differential equation technique to prove convergence of the algorithm in the synchronous update case. We provide simulation results using the NIST simulatorto show that the algorithm is able to track the max-min fair rates for slowly varying random available link bandwidths