OBJECTIVES: To analyze cost-effectiveness of Ferrum Lek (Ferrum III) versus Fenuls (Ferrum II) for iron-deficient anemia in elderly patients with gastrointestinal comorbidy in Russian health care system. METHODS: Randomized multi-center study of 132 ambulatory patients (60-86 years old, mean age 69.11 ± 6.39; 102 (77.27%) were females). Criteria for anemia was decreasing of hemoglobin (Hb) level below 110 g/L. Sixty-six patients received either Ferrum Lek (200 mg daily) or Fenuls (200 mg daily). Duration of treatment was 6 weeks. Criteria of effectiveness were: normalization of Hb level; increasing levels of Hb and Fe in plasma; adverse effects at day 42 after start of treatment. The cost-effectiveness ratio (CER) was calculated (cost of 1 g/L Hb increasing). RESULTS: At follow-up Hb level increases in Ferrum Lek group was 30.1 g/L (12.3 – 88.4) and 19.8 g/L (4 – 39) in Fenuls group. Normalization of Hb level (110 g/L) was achieved in 62 (93.94%) patients in Ferrum Lek group and in 53 (80.3%) patients in Fenuls group. Targeted Hb level (120 g/L) was achieved in 54 (81.82%) patients in Ferrum Lek group and in 36 (54.55%) patients in Fenuls group. Drop-outs due to adverse effects were: 1 patient in Ferrum Lek group and 9 patients in group. Gastrointestinal adverse effects occurred significantly more often in Fenuls group than in Ferrum Lek group (constipation in 21.2% and 1.5% patients, gastric complaints in 28.8% and 6% respectively). The cost per achieving targeted Hb level in Ferrum lek group was 4255.68 rubles and 5990.76 rubles in Fenuls group. Mean cost of 1 g/L Hb increasing is 144.05 (49.8 - 287.7) rubles with Ferrum Lek and 224.72 (69.61 - 896.6) rubles with Fenuls. CONCLUSION: Ferrum Lek is cost-effective medicine for treating iron-deficient anemia in elderly patients with gastrointestinal co-morbidities in comparison with Fenuls.