[en] Sixty-six rabbits, with no history of vaccination against myxomatosis and which had died of pulmonary lesions, were submitted for virological and serological tests for Myxoma virus (MV) infection and for bacteriological examinations. At post mortem, the diagnoses based on observed lesions were as follows: acute haemorrhagic pneumonia (38%); acute suppurative bronchopneumonia (35%); and fibrinohaemorrhagic bronchopneumonia with fibrinous pleuritis (27%). MV was isolated from 10% of the rabbits, mainly from those with acute haemorrhagic pneumonia. Serological evidence of MV infection was demonstrated in 44% of rabbits. Pathogenic bacteria species isolated from lungs were Pasteurella (spp. and multocida), Escherichia coli, Bordetella bronchiseptica and Pseudomonas aeruginosa, respectively, from 41, 11, 7 and 6% of samples. No relationship could be established between the presence of specific antibodies to MV and the observed pulmonary lesions or the results of the bacteriological examinations. A significant trend was established between the severity of the lesions and the results of the bacteriological examinations.