Cystic fibrosis (CF), once known as an untreatable fatal disease in early childhood, is now recognized as a fairly manageable disease but with a primary morbidity dominated by persistent lung infections. Our team and others have shown that bacterial volatile molecules in human breath represent a substantive diagnostic potential for lung infections. The focus of almost all breath research in CF, including ours, has been on two bacterial pathogens (Pseudomonas aeruginosa and Staphylococcus aureus). Here, we propose to target three additional pathogens (Haemophilus influenza, Stenotrophomonas maltophilia, and Burkholderia cepacia complex) that are common for patients with CF and are also broadly relevant to pneumonia in children. My scientific approach spans the careful testing of the molecules produced by bacterial cultures as well as breath of patients with CF. The expected outcomes (biomarker signatures) will provide clinical utility in the diagnosis of these pathogens as well as monitoring antimicrobial therapy efficacy. In addition, the signatures will likely provide a greater understanding of pathogen metabolism.