A survey of 51 people who work on trawlers was carried out to describe injecting and sexual behaviour and the prevalence of HIV and HCV antibody. All crew members who were departing from an Australian port during the last week of February 1996 to work on trawlers were asked to complete a brief, self-administered questionnaire and provide a finger prick blood sample. Questionnaires were received from 51 (77%) and blood samples from 45 (68%) of the 66 crew from 15 vessels. Almost half the respondents reported ever injecting illicit drugs. No respondents had HIV antibody while 27% had HCV antibody detected. Among 20 injecting drug user (IDU) respondents, the prevalence of HCV was 55% (95% CI 32%-77%). Twelve respondents reported new sex partners in the past month of whom half reported no condom use with these sex partners. The survey emphasises the diversity of the IDU population in Australia. Yet it would appear that regardless of the sub-population surveyed that HCV is endemic among IDUs in Australia. Effective HCV prevention programs targeted specifically for these (and other) sub-populations of IDUs should be devised.