The objective of this study was to evaluate the presence of indicators of aspiration in previously healthy infants with respiratory syncytial viral (RSV) bronchiolitis who experienced rapid deterioration in their respiratory status. Lipid-laden macrophage index (LLMI) was assessed in 6 previously healthy infants with RSV bronchiolitis and no prior history of aspiration, who had a rapid deterioration of their respiratory status requiring mechanical ventilation. Five of 6 infants had a LLMI of more than 100, a level that is very suggestive of aspiration. We conclude that aspiration is likely to play a role when rapid deterioration occurs in infants with RSV bronchiolitis.