The protist Giardia duodenalis belongs to the kingdom Protozoa, phylum Metamonads, order Diplomonadida, family Hexamitidae, and genus Giardia. Members of this genus inhabit and parasitize on the intestinal wall of different species of mammals, birds, reptiles, amphibians and fish, and are distributed throughout the world. This parasite appears in two forms in the host, namely the vegetative (mobile) form, i. e., the trophozoite and the cyst (immobile, invasive form). Although invasions with this parasite are often asymptomatic, they can still cause a disease in susceptible groups of animals that can rarely end up fatally. G. duodenalis species complex contains several genetic groups described as groups A-H, some of which are zoonotic. Clinical signs of the disease appear about ten days after the invasion, and are characterized by diarrhea, loss of appetite, and therefore weightloss. The main source of invasion is contaminated food and water. Spread occurs by fecal route, mutual contact of animals by licking, drinking contaminated water, food. The disease can be diagnosed by coprological examination with sedimentation, flotation and the SAFC method (sodium acetate, acetic acid, formalin and diethyl ether) by microscopic finding of cysts and/or trophozoites, and direct immunofluorescence by fluorescent microscope. In addition direct immunochromatographic tests and direct immunoenzyme assay have been developed on the market, as well as PCR,. The text describes individual methods, their advantages and disadvantages. The most commonly used are rapid tests based on immunoenzyme and immunochromatographic principle, however the gold standard in the diagnosis of this parasitic disease is coprological examination.