The effect of electrolyte on the rate of intramolecular electron transfer (ET) was analyzed within the framework of ionic association. A unified approach combining the ionic atmosphere and specific ion pairing contributions to the reorganization energy has been developed. The weighing of the free ion and ion pairing contributions is based on the appropriate mass action law. In the limit of weak association the model converges to the Debye-Huckel-Bjerrum picture of electrolytes. In the limit of strong association the ion-pairing dominates. In accordance with experiment, this results in a remarkable decrease of ET rates even at very low electrolyte concentrations. (C) 2002 Elsevier Science B.V. All rights reserved.