L-Arginine is one of the most commonly used and most generally applicable suppressors of protein aggregation. Its effect as enhancer of in vitro protein refolding was serendipitously discovered two decades ago. This article aims at giving a brief overview about the discovery of the arginine effect, the range of its applications that have been explored over the past two decades, and of the current state of the discussion regarding the mechanisms responsible for the action of L-arginine as suppressor of aggregation.