Increased intracranial pressure may result in the Cushing response. We applied a short pulse of pressure to the cranial cavity of anesthetized cats which were intubated, curarized, ventilated, and the cranium exposed to an 80- to 100-msec pulse of pressure at 5.3 atm. The following significant increases developed: Intracranial pressure rose from 7.4 +/- 1.5 to 150.6 +/- 19.4 mm Hg, systolic arterial peak pressure from 130.7 +/- 8.1 to 299.0 +/- 11.4, pulmonary peak pressure from 18.9 +/- 1.9 to 42.9 +/- 4.9. Alveolar lavage protein in controls was 6.7 +/- 0.4 mg/g lung compared to 11.9 +/- 2.0 in the experimental group. Extravascular lung water/dry weight ratios increased from 3.36 +/- 0.04 in controls to 3.51 +/- 0.09 but varied inversely with pulmonary systolic peak pressure (r = 0.59). These results showed that a pulse of pressure applied to the cranium of cats produced lung edema which was inversely related to pulmonary artery pressures.