The RANCH Project (Stansfeld et al., 2003) is a large EC-funded project which is examining dose-response relationships between road traffic and aircraft noise exposure and children’s cognition and health. Central to the project are three parallel field studies which have been carried out in the UK, Spain, and the Netherlands. For the field studies children’s cognitive performance was assessed by means of a battery of tests which were group-administered in the children’s classrooms. An obvious shortcoming of this approach is that children attending chronically noise-exposed schools are also more likely to be tested in conditions of acute noise. It might therefore be the case that any difference observed between chronically noise-exposed and non chronically noise-exposed groups may be due to the effects of acute rather than chronic noise. This issue has been addressed in the field studies by measuring the acute noise exposure at the time of testing and adjusting for this in the analysis of the data. Given its importance for the overall RANCH study, it was decided to further examine this issue through an experimental sub-study. The results from the field studies indicated that there were associations between aircraft noise, but not road traffic noise, and children’s performance on tests of reading (Clark et al., 2003) and episodic memory (López-Barrio et al., 2003). Children exposed to higher levels of chronic noise performed significantly worse than those exposed to lower levels of chronic noise. The experimental sub-study therefore focussed on these tests and systematically manipulated the chronic and acute noise exposure. Each of these two variables had two levels, giving rise to four groups: high chronic noise – acute noise, high chronic noise – no acute noise, low chronic noise – acute noise, low chronic noise – no acute noise. In order to control the noise conditions all testing took place in a mobile sound-attenuated testing laboratory which was taken to each school. For the acute noise conditions the children heard a recording of aircraft noise which had been recorded in one of the UK RANCH schools. In the case of the memory test, while the acute noise conditions for the encoding phase were manipulated, for the retrieval phase all children performed the test in non acute noise conditions. For the RANCH field studies children were selected from schools which were assigned to categories depending upon their exposure to road traffic and aircraft noise exposure. The children who were selected for the substudy were selected from two groups: those having low road traffic noise combined with low aircraft noise and those having low road traffic noise combined with high aircraft noise. In order to make the sample for the substudy more homogeneous all children were excluded who had either special educational needs or for whom English was not the main language spoken at home. There were a total of 100 participants, all being children who had taken part in the UK RANCH field study. The children were 10-11 years old. The test materials were the same as those which had been used in the UK field study. The reading test used was the Suffolk Reading Scale (Hagley, 1987). This is a test of reading comprehension which is widely used in the UK. Episodic memory was tested by means of a test adapted from the Child Memory Scale (Cohen, 1997). This had two parts, firstly a test of cued recall which is scored separately for specific correct pieces of information and also for more general conceptual recall. The second part is a test of recognition memory in which the children were required to indicate whether the answer to a series of questions was yes or no. The tests were administered in a fixed order and children were tested in pairs. The main prediction from the study is that of the two non acutely noise exposed groups, that group which is exposed to high chronic noise will perform worse than the low chronic noise group. The data from this study is currently being scored and analysed. The findings will be reported and the implications, both for the RANCH Project and more widely, will be outlined.