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The three studies in this thesis examine the effects of chronic exposure to aircraft noise on primary aged school children's cognition, motivation and health. The main aim of this thesis was to test whether the cognitive effects previously found in children are attributable to noise exposure and to test possible mechanisms. The major study (Studies 1 & 2) in the thesis is a repeated measures field study in which the cognitive performance and stress responses of children attending four schools exposed to high levels of aircraft noise (>66 dBA 16hr outdoor Leq) were compared with children attending four matched control schools exposed to lower levels of aircraft noise (<57 dBA 16hr outdoor Leq) around Heathrow Airport in West London. Measures included: reading comprehension, sustained attention, motivation, long and short term memory, noise annoyance, self reported stress, depression, anxiety and attributional style. Follow-up measures were taken after a period of one year. The results of the repeated measures study indicate that chronic exposure to aircraft noise was significantly associated with: a) impaired reading comprehension; b) impaired sustained attention; c) higher noise annoyance and d) raised self-reported stress adjusting for age, deprivation and main language spoken at home. Contrary to previous findings, chronic exposure to aircraft noise did not affect long term memory and motivation. These results do not support the hypotheses that either sustained attention or learned helplessness mediate the effects of noise on cognition in children. Within subjects analyses indicate that children's development in reading comprehension may be adversely affected by chronic aircraft noise exposure. Noise annoyance remains constant over a year with no strong evidence of adaptation. The final study in this thesis (Study 3), is a multi-level modelling study in which the National Standardised Scores (SATs study) for Key Stage 2 in Mathematics, Science and English were analysed in relation to aircraft noise exposure around Heathrow Airport for 11,000 scores of children aged 11. These results of the SATs study suggest that chronic exposure to aircraft noise is associated with school performance in reading and mathematics in a dose-response function after adjustment for school effects, but that this association is influenced by socio-economic factors. Taking all these results together it has been concluded that chronic aircraft noise exposure is a likely contributing factor that leads to impaired cognition and raised stress responses in children. The complex interrelationship between child performance and health, environmental stressors such as noise exposure and socio-economic status needs to be theoretically considered and empirically examined in the future.