Primary graft dysfunction (PGD) is responsible for significant morbidity and mortality after lung transplantation and The International Society for Heart and Lung Transplantation (ISHLT) Working Group on PGD has recently reported standardized consensus criteria, based on the recipient arterial blood-gas analysis and chest X-ray findings, to define PGD and determine its severity (grade range, 0-3). The grading system has been shown to predict post-transplant outcomes; however, further evaluation and refinement of the validity of the grading system is an important next step to enhance its utility. In this review, we describe advantage and disadvantages of the current PGD grading system based on series of analyses we have conducted and possible options for its potential refinement. The suggested revisions are (1) additional assessment time points at 6 and 12 hours should be included, (2) only bilateral infiltrates on chest X-ray (not unilateral infiltrates) should be considered as an infiltrate in bilateral lung transplants, (3) information from the chest X-ray is useful within 6 hours of final lung reperfusion (T0) but is not necessary to classify grade 3 at 12 to 72 hours, (4) apply PGD grade to single and bilateral lung transplant separately, (5) all extubated patients should be considered as grade 0 to 1, (6) note if PGD grade is being defined by specific inclusion and exclusion criteria, including extubation, with clear chest X-ray, on nitric oxide or extracorporeal membrane oxygenation. Although, further evaluations of the PGD definition and grading system are needed, the suggested refinements in this review may further enhance the reliability and validity of the PGD grading system as an important new lung transplant study instrument.