Giardia duodenalis (syn. G. intestinalis, G. lamblia) is a cosmopolitan flagellate organism belonging to the most common intestinal protozoan parasites of humans and animals. Great genetic heterogeneity has been found within G. duodenalis, where only genotypes representing assemblages A and B have zoonotic potential. Fecal samples (447 specimens) obtained from 232 humans in West-central region of Poland were examined by microscopy and PCR. The total prevalence of Giardia in humans was 1.3%. DNA was extracted from three positive fecal samples and PCR products were obtained after amplification using the beta-giardin primers G7 and G759. Sequence and phylogenetic analyses showed that G. duodenalis isolates from humans belonged to A and B genotypes. Moreover, three subgenotypes, including a cosmopolitan subgenotype A2 and two new subgenotypes A and B were detected.