Respiratory oscillometry measures impedance during tidal breathing and is a sensitive marker of smaller airway function. Recent consensus documents provide a framework for the clinician to incorporate this lung function test into routine clinical practice. Oscillometry has an established role in pediatric respiratory medicine. In adults, an abnormal oscillometry result relates to patient symptoms and clinically important outcomes especially in asthma and chronic obstructive pulmonary disease. There is increasing interest in the role of oscillometry when monitoring patients longitudinally including after lung transplantation, and a greater appreciation of intrabreath analysis and the detection of dynamic elastance.