Background: Asthma patients using high cumulative doses of oral corticosteroids (OCSs) are at risk of serious adverse events and are increasingly being treated with steroid-sparing asthma biologics. However, it is unknown whether prescribing these expensive biologics is always justified. Objectives: This study aimed to (1) assess the prevalence of asthma patients using high cumulative doses of OCSs, (2) explore the role of suboptimal inhaler therapy, and (3) estimate the proportion of patients to whom asthma biologics might be prescribed unnecessarily. Methods: All adults (n = 5,002) with at least 1 prescription of high-dose inhaled corticosteroids (≥500-1,000 mcg/day fluticasone-equivalent) and/or OCSs (GINA step 4-5) in 2010 were selected from a pharmacy database including 500,500 Dutch inhabitants, and sent questionnaires. Of 2,312 patients who returned questionnaires, 929 had asthma. We calculated the annual cumulative OCS dose and prescription fillings and checked inhaler technique in a sample of 60 patients. Patients estimated to have good adherence and inhaler proficiency who still required high doses of OCSs (≥420 mg/year) were considered candidates for initiating biologic treatment. Results: 29.5% of asthma patients on GINA 4-5 therapy used high doses of OCSs, of which 78.1% were likely to have poor therapy adherence or inadequate inhaler technique. Only 21.9% were considered definitive candidates for biologic therapy. Conclusion: High OCS use in Dutch GINA 4-5 asthma patients was common. However, in 4 out of 5 patients adherence to inhaled corticosteroid therapy and/or inhalation technique was considered suboptimal. Since optimizing inhaler therapy may reduce the need for OCSs, this should be mandatory before prescribing expensive steroid-sparing drugs.