The present study reports the results of 2 surveys of the first behavioural surveillance system (BSS) set up to monitor sexually-related risk behaviours practised by Hong Kong-China cross-border travellers. The 2 studies interviewed 1263 and 1448 male adult Hong Kong residents in 1997 and 1998 respectively. About one-third of the respondents had had sexual intercourse with a commercial sex worker (CSW) in the past 6 months; about 20% had had sexual intercourse with a CSW or a non-regular sex partner in a single trip; about 35-40% of the CSW clients had not used a condom during the intercourse and about 20% of the respondents reported that they had contracted STD. When the results of the 2 surveys were compared, no significant changes in the outcomes of the surveillance indicators were detected; instead, some unfavourable changes in terms of condom use were observed. The effectiveness of the relevant prevention programmes in Hong Kong is not evident.