2-Pyrrolidone derivatives are provided as preservatives for topical formulations, particularly for ophthalmic, otic, and nasal formulations. N-octyl-2-pyrrolidone, without any other preservative or preservative aid in an isotonic pH 7.5 formulation, provided sufficient preservation to comply with the European Pharmacopoeia 5.0 standards in addition to the United States Pharmacopoeia 24 standards for parenteral and ophthalmic preparations. On the other hand, N-dodecyl-2-pyrrolidone requires a second anti-microbial agent to achieve such preservation standards.