Summary The use of antibiotics in aquaculture may cause development of antibiotic resistance among pathogens infecting cultured animals and humans. However, this is a recent issue and has not yet been thoroughly investigated. Furthermore, there is limited knowledge about the environmental effects of antibiotic use in aquaculture. It is well known that antibiotics are commonly used in shrimp farming to prevent or treat disease outbreaks, but there is little published documentation on details of usage patterns. This study, conducted in 2000, shows that a large proportion of shrimp farmers along the Thai coast used antibiotics in their farms. Of the seventy-six farmers interviewed, 74% used antibiotics in shrimp pond management. Most farmers used them prophylactically, some on a daily basis, and at least thirteen different antibiotics were used. Many farmers were not well informed about efficient and safe application practices. A more restrictive use of antibiotics could have positive effects for the individual farmer and, simultaneously, decrease impacts on regional human medicine and adjacent coastal ecosystems. It is likely that dissemination of information could contribute to a decreased use of antibiotics, without decreasing the level of shrimp production.