The Welsh laboratory emphasizes research in two main areas. The first focuses on cystic fibrosis (CF), a common lethal genetic disease in which lung disease is the major cause of morbidity and mortality. Welsh and his colleagues are discovering the pathogenesis of airway disease, elucidating the impact of environmental exposures on disease pathogenesis and respiratory defenses, and developing novel treatments. The second focuses on neurodegenerative diseases, including Parkinson’s disease and Alzheimer’s disease. Welsh and his colleagues are investigating the pathophysiological basis of protein aggregates and developing treatments to prevent or delay the progressive neuron loss.