Conjugates of an interleukin-2 (“IL-2”) moiety and one or more nonpeptidic, water-soluble polymers are provided. Typically, the non-peptidic, water-soluble polymer is poly(ethylene glycol) or a derivative thereof. Also provided, among other things, are compositions comprising conjugates, methods of making conjugates, methods of administering compositions to an individual, nucleic acid sequences, expression systems, host cells, and methods for preparing IL-moieties.