Abstract: An total genomic DNA probe of Giardia lamblia labelled with biotin was prepared.High sensitivity and speciality of the probe were demonstrated in the dot blot test.A hybridisation signal with 10 ng of G.lamblia DNA,and 103 trophozoites or cysts was obtained by using this probe.There was no cross-reation with the closely related DNA from Trichomonas vaginalis,Entoamoeba histolytica and Toxoplasma gondii.Also,no crosshybridisations were found with the liver cells DNA from BABL/c mice as well as the fecal supernatant of G.lamblia infected subject.This probe can be used to detect G.lamblia and identify different isolates of this protozoa.