The objective of this study was to determine the association between continuity of care and emergency room visits/hospital care for patients with asthma. A population-based study was conducted using administrative healthcare datasets obtained from Alberta Health and Wellness, Alberta, Canada. The 4-year study period extended from April 1, 1996 to March 31, 2000, and took place at the Palliser Health Region in Alberta, Canada, which has a population of 88,000 people. A population-based sample of 2774 patients, diagnosed with asthma between ages 5 and 45 with two or more office visits for asthma and who lived in the Palliser Health Region for 2 consecutive years during the study period, was studied. The main outcome measure was the association of continuity of care with hospitalizations and emergency room visits for patients with asthma. Continuity of care was the proportion of total physician visits made to the most frequently visited physician. High continuity of care was associated with a decreased risk of an emergency visit (OR = 0.24: 95% CI 0.19-0.29), number of emergency visits (RR = 0.37; 95% CI 0.32-0.42), decreased risk of number of hospitalizations (RR = 0.69; 95% CI 0.54-0.89), and total days in hospital (average difference = 0.77; 95% CI 0.63-0.95), but not with ever hospitalized. High continuity of care was associated with a 60%-75% reduction in emergency room visits and an approximate 25% reduction in number of hospitalizations in patients with asthma. Interventions to improve continuity of care could have the potential to improve care and reduce cost.