Corrosion affects commercial float glass production and glasses used to contain high level nuclear waste. In order to prevent the corrosion it is necessary to understand the composition of the corroded glass and the corrosion mechanism taking place. SIMS depth profiling lends itself well to monitoring the compositional changes that occur during the corrosion process. However, most studies have analysed glass that has been corroded using accelerated ageing conditions. In this work a soda-lime glass has been aged at room temperature under known atmospheric humidity for increasing periods of time. The aged glass has then been depth profiled using a low energy (1 keV) Cs beam monitoring both the sodium and hydrogen signals concurrently. The depth profiles show that in the region directly below the glass surface that is severely depleted in sodium, there is an increased level of hydrogen compared to the bulk glass indicating an increase in the water content within this region. (c) 2006 Elsevier B.V. All rights reserved.