There were studied three dead lambs after a diarrhea syndrome aged between two and three months in Şag place, Timiş County, where histological examinations were performed. The fragments of tissues were fixed in alcohol 800 for 7 days, after which they were washed, dehydrated and paraffin embedded, sectioned at microtome, yielding a 5 micrometer sections which were attached to glass slides. Sections were processed by method hematoxylin - eosin and Mallory trichromic method. At the histological level after performing two hematoxylin staining methods - eosin and Mallory trichromic method, there were highlighted: atrophy and degeneration of enterocytes, basement membrane thickening, areas of necrosis, infiltration of the mucosa and submucosa with histiocytes and polymorphonuclear. Giardia was found attached to the edge of enterocytes, causing infiltration in the lamina propria. The infection with Giardia spp. in lambs following the macroscopic examination, there was observed intestinal content congestions, diarrhea, with mucus, lining in the presence of excess gas.