Acrolein (CAS No. 107-02-8) was evaluated for acute inhalation toxicity in male Sprague-Dawley Spartan rats (7/exposure group) administered single dynamically generated whole-body exposures to average analytic vapor concentrations of 14.5, 41.5, 93.5, and 251 ppm for up to 30 minutes. During exposures and a 15-minute post- exposure venting period, the animals were observed continuously for behavioral anomalies and sensory irritation, including altered reflexes, eye and/or nasal irritation, and or respiratory irregularities. Treatment was associated with clinical signs of toxicity including teary and squinted eyes, nasal discharge, labored breathing, gasping, and prostration at all levels of exposure; treatment also dampened righting, blink, and pain reflexes at exposures of 41.5 ppm or greater. Bodyweights were low normal based on comparison with historical controls, and mortality was consistent with a 30-minute LC50 of 60 ppm. Additionally, severity, time to onset, progression, and duration of the toxic response were each correlated with dose. Immediate necropsy of study lethalities upon their discovery revealed treatment-related gross pathology including congestion of nasal turbinates (41.5 ppm), failure of lungs to collapse on incision with a dark mottled and congested appearance of apical and cardiac regions of the lungs (41.5 ppm, 1/7), accumulations of exudate around nose and mouth (93.5 ppm, 7/7; 251 ppm, 7/7), mucopurulent or mucohemorrhagic rhinitis (93.5 ppm, 7/7; 251 ppm, 7/7), pulmonary congestion and hemorrhage (93.5 ppm, 7/7; 251 ppm, 7/7), gaseous distention of the stomach (93.5 ppm, 7/7; 251 ppm, 7/7), congestion of liver and kidneys (93.5 ppm, 7/7; 251 ppm, 1/7), pulmonary edema (251 ppm), and hydrothorax (251 ppm). None of 7/7 terminally sacrificed survivors of a 14.5 ppm exposure exhibited any treatment-related gross pathology, while survivors of 41.5 ppm exposures hadcatarrhal rhinitis on Day 15 terminal necropsy.