Obstructive lung disease and, in particular, asthma are the most common lung diseases that must be excluded in divers,20due to concern about the possible occurrence of pulmonary barotrauma and arterial gas embolism as a result of air trapping.21–23 Moreover, breathing cold, dry air during diving, as well as the greater demands made on the respiratory system underwater due to the physical exertion required, can lead to bronchospasm.14 In our diving population, asthma and other obstructive airways disease associated with air trapping are contraindications to commence or continue diving. However, an earlier study by Crosbie at al5 described a diver population in whom, despite abnormal spirometry manifesting as a low FEV1%, further evaluation revealed no evidence of obstructive airways disease. These divers had elevated FVC and TLC, a normal FEV1, and no air trapping (normal RV/TLC). Crosbie and colleagues,4–5 named this phenomenon divers’ “large lungs.” It was shown that in divers up to the age of 30 years, FVC increased with years of diving and with increased diving depth.4–5 In contrast to this, there was no change in FEV1. This resulted in a large FVC and a decrease in the FEV1%, with no evidence of air trapping. It was noted, however, that in divers >30 years old, FVC declined despite continued diving, even when age was taken into account.,4–5 This decrease may be related to diving-induced structural changes in the lung beyond the reduction in the elastic recoil of normal lungs due to aging.