We evaluated temporal trends in hospitalization for bronchiolitis found among Canadian children for 1980-2000. The rate of hospital admission increased in all provinces over the 2 decades for all age groups but was highest in those aged <6 months. The mean length of stay decreased from 5.4 to 3.1 days (mean rate of decrease, 0.13 days/year; P<.0001). Because a concurrent increase in other respiratory diagnostic codes was not seen, it is unlikely that physician practice variation could explain this consistent trend over almost 2 decades, which may indicate a change in disease prevalence or severity.