Rationale: Asthma clinical guidelines suggest written asthma action plans are essential for improving self-management and outcomes.Objectives: To assess the efficacy of written instructions in the form of a written asthma action plan provided by subspecialist physicians as part of usual asthma care during office visits.Methods: A total of 407 children and adults with persistent asthma receiving first-time care in pulmonary and allergy practices at 4 urban medical centers were randomized to receive either written instructions (n = 204) or no written instructions other than prescriptions (n = 203) from physicians.Measurements and Main Results: Using written asthma action plan forms as a vehicle for providing self-management instructions did not have a significant effect on any of the primary outcomes: (1) asthma symptom frequency, (2) emergency visits, or (3) asthma quality of life from baseline to 12-month follow-up. Both groups showed similar and significant reductions in asthma symptom frequency (daytime symptoms [P , 0.0001], nocturnal symptoms [P , 0.0001], b-agonist use [P , 0.0001]). There was also a significant reduction in emergency visits for the intervention (P , 0.0001) and control (P , 0.0006) groups. There was significant improvement in asthma quality-of-life scores for adults (P , 0.0001) and pediatric caregivers (P , 0.0001).Conclusions: Our results suggest that using a written asthma action plan form as a vehicle for providing asthma management instructions to patients with persistent asthma who are receiving subspecialty care for the first time confers no added benefit beyond subspecialtybased medical care and education for asthma.Clinical trial registered with www.clinicaltrials.gov (NCT 00149461).