Background Asthma is a common chronic respiratory condition, the diagnosis of which depends on symptoms and objective evidence of variable airflow obstruction or airway hyperresponsiveness. The proportion of people who have had objective pulmonary function testing around the time of diagnosis and factors associated with receiving testing are not well understood. Methods A retrospective cohort study was conducted using the health administrative data of all individuals aged 7 years and older with newly physician-diagnosed asthma living in Ontario, Canada between 1996 and 2007. Receipt of pulmonary function testing in the peridiagnostic period was determined and examined across patient sociodemographic and clinical factors. Results Only 42.7% (95% CI, 42.6%-42.9%) of the 465,866 Ontarians newly diagnosed with asthma received pulmonary function testing between 1 year prior and 2.5 years following the time of diagnosis. In adjusted analyses, individuals 7 to 9 years old and those 70 years or older were less likely to receive testing than younger adults, individuals in the lowest neighborhood income quintile were less likely to receive testing than those in the highest, and individuals seeing a medical specialist were more likely to receive testing than those seeing only a general practitioner. Conclusions Less than one-half of patients with new physician-diagnosed asthma in Ontario, Canada received objective pulmonary function testing around the time of diagnosis. Further study is needed to determine why more pulmonary function testing is not being used to diagnose asthma and how barriers to its appropriate use can be overcome.