Giardiasis is the most common waterborne parasitic infection of the human intestine worldwide.The etiological agent,Giardia duodenalis(syn.G.intestinalis,G.lamblia),is a flagellated,binucleated protozoan parasite which infects a wide array of mammalian hosts.Human giardiasis is a true cosmopolitan pathogen,with highest prevalence in developing countries.Giardiasis can present with a broad range of clinical manifestations from asymptomatic,to acute or chronic diarrheal disease associated with abdominal pain and nausea.Most infections are self-limiting,although re-infection and chronic infection can occur.Recent evidence indicating that Giardia may cause chronic post-infectious gastrointestinal complications have made it a topic of intense research.The causes of the post-infectious clinical manifestations due to Giardia,even after complete elimination of the parasite,remain obscure.This review offers a state-of-the-art discussion on the long-term consequences of Giardia infections,from extra-intestinal manifestations,growth and cognitive deficiencies,to post-infectious irritable bowel syndrome.The discussion also sheds light on some of the novel mechanisms recently implicated in the production of these postinfectious manifestations. Giardiasis is the most common waterborne parasitic infection of the human intestine worldwide.The etiological agent, Giardia duodenalis (syn.G. intestinalis, G.lamblia), is a flagellated, binucleated protozoan parasite which infects a wide array of mammalian hosts. Human giardiasis is a true cosmopolitan pathogen, with highest prevalence in developing countries. Giardiasis can present with a broad range of clinical manifestations from asymptomatic, to acute or chronic diarrheal disease associated with abdominal pain and nausea. Host infections are self-limiting, although re-infection and chronic infection can occur. Reproduction indicating that Giardia may cause chronic post-infectious gastrointestinal complications have made it a topic of intense research. causes causes of the post-infectious clinical manifestations due to Giardia, even after complete elimination of the parasite, remain obscure.This review offers a state-of-the-art discussion on the long-term consequences of Giardia infections, from e xtra-intestinal manifestations, growth and cognitive deficiencies, to post-infectious irritable bowel syndrome. The discussion also sheds light on some of the new mechanisms recently implicated in the production of these post infectious manifestations.