Background: Anecdotal evidence reported an outbreak of symptoms on Fraser Island during the late 1990s similar to those expected from exposure to dermotoxins found in the cyanobacterium L. majuscula. This coincided with the presence of a bloom of L. majuscula. Methods: Records from the Fraser Island National Parks First aid station were examined. Information on cyanobacterial blooms at Fraser Island were obtained from Queensland National Parks rangers. Results: Examination of first aid records from Fraser Island revealed an outbreak of symptoms predominantly in January and February 1998. Conclusion: During a bloom of L. majuscula there were numerous reports of symptoms that could be attributed to dermotoxins found in L. majuscula. The other four years examined had no L. majuscula blooms and the number of L. majuscula symptoms was much reduced. These cases comprised a high percentage of the cases treated at the first aid station.