Airway basal cells (BC) function as progenitor cells capable of differentiating into ciliated and secretory cells to replenish the airway epithelium during physiological turnover and repair. The objective of this study was to define the role of Notch signaling in regulating human airway BC differentiation into a pseudostratified mucociliated epithelium. Notch inhibition with -secretase inhibitors demonstrated Notch activation is essential for BC differentiation into secre-tory cells and ciliated cells, but more so for the secretory lineage. Sustained Notch activation via lentivirus expression of the intracellular domain of each Notch receptor (NICD1-4) demonstrated that the Notch 2 and 4 pathways have little effect on BC differentiation, while activation of the Notch1 or 3 pathways has a major influence, with persistent expression of NICD1 or 3 resulting in a skewing toward secretory cell differentiation with a parallel decrease in ciliated cell differentiation. These observations provide insights into the control of the balance of BC differentiation into the secretory vs ciliated cell lineage, a balance that is critical for maintaining the normal function of the airway epithelium in barrier defense against the inhaled environment.