These V/Q images are of the lungs of a healthy university freshman, 18 years old who was picked up as having an abnormal chest x-ray at the university entrance physical examination. The x-ray showed a unilateral hyperlucent lung on the left side. Pulmonary function tests and blood gases were almost within normal limits. There was no history of subjective complaints in performing physical exercises at school. He had grown in a normal environment without any contributory past history of significant illness. This examination was the first time he had been checked medically.