In this report, we review the hospital course of four patients who presented with an acute pulmonary syndrome after inhaling freebase cocaine and compare them with previously described case reports. Two patients had prolonged inflammatory pulmonary injury associated with fever, hypoxemia, hemoptysis, respiratory failure, and diffuse alveolar infiltrates. Lung tissue specimens from both patients revealed diffuse alveolar damage, alveolar hemorrhage, and interstitial and intraalveolar inflammatory cell infiltration notable for the prominence of eosinophils. Immunofluorescent staining performed on one of the biopsy specimens showed a striking deposition of IgE in both lymphocytes and alveolar macrophages. Both patients were treated with systemic corticosteroids and rapidly improved. In contrast, two patients presented acutely with diffuse pulmonary alveolar infiltrates associated with dyspnea and hypoxemia, but without fever, and within 36 h of discontinuing cocaine their pulmonary infiltrates and symptoms had spontaneously resolved. Our report further supports the finding that an acute pulmonary syndrome can occur after inhalation of freebase cocaine. Furthermore, the lung injury may respond to systemic corticosteroid therapy when it is associated with a prominent inflammatory cell infiltration.