A dot-ELISA technique for the detection of G. lamblia specific antigen in stool eluates of clinical cases of giardiasis was developed and evaluated employing monospecific antibodies to a G. lamblia specific coproantigen with a molecular mass of 66 kDa. The assay detected 22 (91.7%) of the 24 microscopically confirmed cases of giardiasis while none of the stool eluates from 20 patients with gastrointestinal parasites other than G. lamblia and 20 apparently healthy subjects had any detectable levels of G. lamblia-specific coproantigen. Of the 25 stool eluates from clinically suspected cases of giardiasis, 13 (52%) were found to contain G. lamblia-specific coproantigen. A 3-month-follow up of five of such cases where stool eluates has antigen detected by dot-ELISA assay, revealed the presence of G. lamblia cysts on repeated stool examinations. All the clinically suspected cases with detectable levels of G. lamblia-specific coproantigen by dot-ELISA were relieved of their clinical symptoms following metronidazole therapy. Single stool eluate examination by dot-ELISA was found to be sufficient to confirm the diagnosis. The dot-ELISA is an easy, rapid, sensitive and specific procedure for confirming the diagnosis of suspected cases of giardiasis. It should be a valuable diagnostic aid under field conditions as well as in the laboratory.