The aim of this study is to examine retrospectively the clinical, biological and treatment features of anemia by vitamin B12 deficiency in the Hematology department of CHU Mohamed VI Marrakech. We report the results of a retrospective study conducted during six years (2005-2010). It included all patients with anemia (with or without thrombocytopenia or leukopenia) associated with vitamin B12 levels <200 pg / ml. One hundred twenty one cases were analyzed. The average age of patients was 62 years (38-89 years) with a female predominance (sex ratio F/M: 1.3). The clinical symptomatology is dominated by pallor (97.5%), cardiovascular signs (46%) and digestive symptoms (34.7%). Neurological signs were noted in 17.3% of cases. The blood count showed anemia (hemoglobin: mean= 6.9 g/dl), macrocythemia (MCV: mean= 109 fl). Leukopenia was noted in 35 patients (29%), thrombocytopenia in 34 patients (28%) and pancytopenia in 21 patients (17,3%). The average vitamin B12 was 72 pg/ml. The causes of B12 deficiency are pernicious anemia (43%), food-cobalamin malabsorption (43%), and in 14% of cases no etiology was found. Gastritis was found in 82.7% of our patients and Helicobacter pylori (HP) infection in 72.7% of cases. Reticulocyte crisis was observed after parenteral administration of hydroxocobalamine within an average of 8 days and normalization of blood counts, in all patients, within an average of 51 days. In patients with HP infection, eradication therapy of HP was performed. The cure rate of the HP is 90%.