Context .- Surgical and pathologic handling of lung physically affects lung tissue. This leads to artifacts that alter the morphologic appearance of pulmonary parenchyma. Objective . -To describe and illustrate mechanisms of ex vivo artifacts that may lead to diagnostic pitfalls. Design .- In this study 4 mechanisms of ex vivo artifacts and corresponding diagnostic pitfalls are described and illustrated. Results . -The 4 patterns of artifacts are: (1) surgical collapse, due to the removal of air and blood from pulmonary resections; (2) ex vivo contraction of bronchial and bronchiolar smooth muscle; (3) clamping edema of open lung biopsies; and (4) spreading of tissue fragments and individual cells through a knife surface. Morphologic pitfalls include diagnostic patterns of adenocarcinoma, asthma, constrictive bronchiolitis, and lymphedema. Conclusion .- Four patterns of pulmonary ex vivo artifacts are important to recognize in order to avoid morphologic misinterpretations.