In an attempt to identify those infants with resolving chronic lung disease of prematurity (CLD) at greatest risk of sudden infant death syndrome or acute life threatening event (SIDS/ALTE), or readmission to hospital following discharge, recordings of arterial oxygen saturation were made on 35 infants. Recordings were collected while the infants were breathing room air. Movement artefact was excluded and the data analysed to provide the mean individual arterial oxygen saturation (MSaO2), and the variability of the mean individual oxygen saturation (delta MSaO2). These data were related to clinical outcome recorded over the three months following investigation. A MSaO2 less than 90% on discharge predicted hospital admission within three months with a sensitivity of 1 and a specificity of 0.76, and SIDS/ALTE with a sensitivity of 1 and a specificity of 0.75. A delta MSaO2 greater than 6% predicted SIDS/ALTE with a sensitivity 0.88 and specificity of 1. Infants with resolving chronic lung disease of prematurity who are at risk of increased morbidity and mortality can be assessed by accurate measurement of mean arterial saturation.