Abstract
This paper provides axiomatic descriptions of social welfare relations, defined on infinite streams of utility, that are consistent with the utilitarian criterion on subsets where maximizing aggregate utility has a clear interpretation: the streams, or their differences, are summable. Besides standard assumptions on efficiency, equity and interpersonal comparability, two axioms are introduced and shown to be necessary and sufficient. A more general version of one axiom suffices to distinguish streams with different long-run averages.