Aims: To determine the occurrence of the human pathogen, Vibrio vulnificus, in south Texas coastal waters. Methods and Results: Coastal waters were sampled monthly between August 2006 and July 2007. Water temperature, dissolved oxygen, pH, salinity, conductivity and turbidity were measured during each sampling event. Culture-based techniques utilizing Vibrio vulnificus agar (VVA) and membrane-Enterococcus indoxyl-beta-d-glucoside agar (mEI) were used to assess the occurrence and levels of V. vulnificus and the faecal contamination indicator group, enterococci, respectively. Vibrio vulnificus isolates were confirmed using colony-blot hybridization with the species-specific VVAP probe. Vibrio vulnificus was isolated at all sites throughout the year even when the water temperature dropped to 9 center dot 71 degrees C. Significant correlations were found between concentrations of V. vulnificus and the abiotic factors, water temperature (P = 0 center dot 002) and dissolved oxygen (P = 0 center dot 028), as well as between concentrations of V. vulnificus and enterococci (P < 0 center dot 001). Conclusions: This study demonstrated the year-round presence of V. vulnificus in coastal waters of south Texas. Significance and Impact of the Study: These findings indicate that the potential for human exposure to the pathogen, V. vulnificus, exists throughout the year. It also suggests that routinely monitored data might be used to predict the occurrence of the pathogen.