RATIONALE: ClinicalTrials.gov is the largest trial registry in the world. Strengthened registration requirements, including federal mandates in 2007, have increased study representation. A systematic evaluation of all registered studies has been limited by the absence of an aggregate data set and specialty-specific search terms. OBJECTIVES: We leveraged a newly transformed database containing annotated data from ClinicalTrials.gov to define the portfolio of interventional clinical research in pulmonary, critical care, and sleep medicine. METHODS: Analysis was restricted to studies registered after September 2007 through September 2010 and defined as "interventional" (n = 40,970). A specialty-specific study data set (n = 2,226) was created using disease condition terms provided by data submitters and medical subject heading terms generated by a National Library of Medicine algorithm. Trial characteristics were extracted and summarized using descriptive statistics. MEASUREMENTS AND MAIN RESULTS: Pulmonary, critical care, and sleep medicine trials composed 5.4% of all interventional studies registered over the 3-year period. In contrast, oncology and cardiovascular disease composed 21.9 and 8.4% of trials, respectively. Within pulmonary trials, asthma and chronic obstructive pulmonary disease were the most studied conditions (27.4 and 21.8% of studies, respectively), and measures of lung function or safety were the most frequent primary outcomes. Nearly two-thirds of trials indicated enrollment of 100 patients or fewer, and a majority of studies were phase II or III trials. The single largest funding source (43.5%) was industry, and study characteristics varied by funding source. CONCLUSIONS: We applied a novel approach to describe the portfolio of interventional clinical research in pulmonary medicine. Our results indicate a disparity between trial representation and the burden of respiratory disease. Resources should be targeted across the spectrum of pulmonary research to address this discrepancy.