Hong Kong played a pivotal role in the international spread of the Severe Acute Respiratory Syndrome (SARS): a doctor who spent the night of 21-22 February 2003 at Hotel 'M' was identified as the index case for four national and international clusters of SARS. In parallel to the international collaborative study led by WHO and United States, a retrospective study on the cohort of German persons staying at Hotel 'M' was conducted. The inclusion criteria covered a period from 21 February to 3 March 2003 to allow the detection of cases possibly due to environmental contamination. In the twenty-one German guests traced as having stayed at Hotel "M" during this period, one case of laboratory confirmed SARS was found. The case history suggests that close vicinity to the index patient may have played a role in transmission. In line with findings of environmental investigations in the hotel, environmental contamination should be considered as a possible source of infection.