Spontaneous pneumomediastinum (SP) unrelated to assisted ventilation is a newly recognised complication of severe acute respiratory syndrome (SARS). The objective of the present study was to examine the incidence, risk factors and the outcomes of SP in a cohort of SARS victims from a community outbreak. Data were retrieved from a prospectively collected database of virologically confirmed SARS patients. One hundred and twelve cases were analysable, with 13 patients developing SP (11.6%) at a mean +/- SD of 19.6 +/- 4.6 days from symptom onset. Peak lactate dehydrogenase level was associated with the development of SP. SP was associated with increased intubation and a trend towards death. Drainage was required in five cases. For patients who survived, the SP and/or the associated pneumothoraces took a median of 28 days (interquartile range: 15-45 days) to resolve completely. In conclusion, spontaneous pneumomediastinum appeared to be a frequent complication of severe acute respiratory syndrome. Further research is needed to investigate its pathogenesis.