The Oklahoma Department of Transportation has been applying silane penetrating water sealers since the late 1970' s to prevent the intrusion of chloride contaminated water in bridge decks. This contaminated moisture causes severe corrosion in reinforcing steel and costly damage to the bridge deck. To determine how silanes perform in the field, Research, Development and Technology Transfer established an evaluation plan. The primary objectives of this study were to monitor the chloride ion content and · corrosion activity in the top mat of reinforcing steel and to evaluate the performance of Portland cement penetrating sealers over five years. Ten bridges treated with silanes were selected for this study along with one untreated bridge. This report discusses the findings as they pertain to these objectives. Tests were performed to assess the physical characteristics of the bridge deck over time and ascertain the presence of silanes years after application. In order to obtain a true picture of the performance of water penetrating silanes over time, it is necessary to have initial data. There was little initial information recorded at the onset of this evaluation. In short, absence of initial conditions makes it difficult to evaluate the long term performance of silane penetrating sealers. Since the time of this evaluation, modifications have been made to the specifications and conditions by which silanes may be applied to bridge decks. Continued monitoring of these bridges decks without critical initial information will not yield more reliable results or information that will be applicable to bridges currently treated with silanes.