The BRFSS Asthma Call-back Survey (ACBS) is a supplemental, in-depth questionnaire administered to respondents of the Behavioral Risk Factor Surveillance System (BRFSS) who report ever having been diagnosed with asthma. It captures detailed information on asthma prevalence, severity, control, medication use, health care utilization (hospitalizations, emergency visits), environmental and occupational triggers, comorbid conditions, quality of life impacts, and demographic characteristics for both adults and children. The survey is created and funded by the CDC's National Center for Environmental Health specifically the Asthma and Community Health Branch and has been conducted annually since its pilot in 2005, with most U.S. states participating each year. Its primary purpose is to provide state level, granular asthma surveillance data that supplement the core BRFSS estimates, enabling public health officials, researchers, and policymakers to monitor trends, evaluate asthma programs, identify high risk populations, and guide resource allocation for prevention and management. Key features include a call-back design (a follow-up telephone interview after the initial BRFSS survey), separate adult and child modules, a large variable set (over 1,000 variables per year) that integrates both ACBS and core BRFSS data, and annual public release files in SAS format for easy analysis. This unique follow-up approach yields richer, clinically relevant insights not available from the standard BRFSS alone.