Capnography is a graphic representation of the carbon dioxide concentration in the airways plotted against time. We report an unusual biphasic-shaped capnogram in a single-lung transplant recipient. In keeping with the only 2 prior reports of which we are aware, we ascribe the unusual biphasic pattern to differential emptying of the native and transplanted lungs. This experience reminds respiratory clinicians of the value of capnometry as a monitoring tool and hopefully will heighten awareness regarding the diagnostic value of usual and unusual capnographic patterns.