Summary. .In this study, hospital admissions for lower respiratory tract illness before two years of age have been documented for all children born in Western Australia in 1986. Admissions data were linked to birth and death records for individual children. Of the total cohort, 5% of non-Abqriginal and 17% of Aboriginal children were hospitalised only once for lower respiratory tract illness; 1% of non-Aboriginal and 11% of Aboriginal children had repeated admissions. Perinatal conditions comprised the greatest proportion of the admissions for non-Aboriginal children, and pneumonia for Aboriginal children. Non-Aboriginal children had decreasing admission rates from the neonatal period onwards, whereas those for Aboriginal children increased. For all children, those of low or high birthweight, male sex and those with young or unmarried mothers or residing in country regions were more likely to be admitted. This research has highlighted potential risk factors for serious respiratory illness in early childhood and has shown the feasibility of using linked data for the total population to formulate and test hypotheses relating to respiratory morbidity.