NODULARIN-related intoxications have been described in a variety of species, including dogs (Main and others 1977, Beasley and others 1989, van Halderen and others 1995, Duy and others 2000, van Apeldoorn and others 2007, Broker and others 2010). Nodularin is a potent hepatotoxin produced by the cyanobacterium Nodularia spumigena , which can be found in brackish waters in cyanobacterial blooms (Dittmann and Wiegand 2006, van Apeldoorn and others 2007). In recent years, a significant increase in cyanobacterial blooms due to anthropogenic eutrophication of the aquatic ecosystem has been observed worldwide (Pitois and others 2001, Smith 2003). Dogs exposed to nodularin by drinking contaminated water show acute signs of intoxication, such as vomiting and diarrhoea, as a consequence of hepatic and renal failure, and intoxication is often associated with death (Nehring 1993, Harding and others 1995). Although an immunotoxic effect of cyanotoxins has been demonstrated experimentally in vitro as well as in sheep and laboratory rodents, so far, there have been no reports describing alterations of the lymphoid organs in carnivores. This short communication describes cases of intoxication after ingestion of nodularin-contaminated water in two dogs showing depletion of the lymphoid organs as well as the classical changes in the liver and kidneys. Two dogs, a six-month-old French bulldog (dog 1) and a five-year-old crossbreed (dog 2), were presented with a clinical history of acute onset of partly haemorrhagic vomiting and depression after being observed drinking bloom-contaminated water from the German Baltic Sea. These dogs, which both showed changes in their lymphoid organs, were two of three dogs examined …