This thesis examined competition for attention resources between cognitive and posture tasks, amongst adult volunteers categorised into three age groups: young (aged between 18 and 32), 60-69 years, and 70 years and over. The,first experimental chapter examined the conflict between a verbal fluency task and continuous walking in a group of44 participants. Walking was shown to be . ''. attentionally demanding for all participants but there was evidence that walking was increasingly demanding with advanced age. The second experimental chapter used similar methods (N = 33) but altered the ph~sical demands of walking with a tray carrying task. The results ofthis study supported the findings ofthe previous experiment and demonstrated that the young and 60-69 year old groups were able to reallocate attention resources during certain task combinations, but the older 70+ group could not. The third and fourth experiments monitored foot positioning ~?uring real and virtual obstacle stepping tasks (N =46 in each experiment). Concurrently with stepping participants carried out either a verbal fluency or digit string reaction time tasks. The young adults stepped more conservatively during the verbal fluency task than any other task, yet the attention demands ofthis task were considered to be the greatest. The 70+ group showed riskier, 'cognitive first' stepping strategies during the verbal fluency task which could account for incidents oftrips in older age. I The final experimen{examined the integration of visual information for controlling postural sway, in visually stable, perturbed, and dark conditions. Participants (N = 30) carried out reaction time tasks in each condition. Different visual integration mechanisms were identified, suggesting that older adults relied less on visual information for postural stability compared to the young adults. Posture stability was also mediated by concurrent cognitive demands.