Of the 120 systemic lupus erythematosus (SLE) patients treated by the authors, two have developed diffuse alveolar haemorrhage. The authors' objective is to present this rare, but severe manifestation. Patients 1 and 2 were 66- and 22-year old women, respectively. Both had SLE with multi-organ involvements including diffuse proliferative lupus nephritis. Before the diagnosis of the disease, both patients had experienced pneumonitis that resolved on corticosteroid treatment. Soon after the diagnosis, respiratory failure, haemoptoea and acute anaemia developed, accompanied by a rapid deterioration in the general condition. Chest radiographs revealed bilateral, diffuse, alveolar infiltrates. The pulmonary haemorrhage temporarily ceased in response to corticosteroid treatment, but both patients later died in consequence of active SLE and mixed bacterial and fungal sepsis. Post mortem examination demonstrated fibrosing alveolitis and alveolar bleeding in Patient 1, and an immune complex deposition-induced alveolocapillary inflammation with alveolar haemorrhage in Patient 2. Diffuse alveolar haemorrhage is a life-threatening manifestation of SLE. Its onset may be preceded by episodes of pneumonitis resolving on corticosteroid treatment. An active diagnostic workup, intensive observation and aggressive immunosuppressive treatment are the cornerstones of the management. The early detection and the active treatment of secondary infections are obligatory. The authors consider the most difficult challenge to be the optimum coordination of the above treatment modalities.