OBJECTIVES: Type I Gaucher disease (GD) is an autosomal recessive disorder caused by a deficiency in β-glucocerebrosidase enzyme, causing hepatosplenomegaly, anaemia, trombocitopenia, bone injuries and other complications. Intravenous enzyme replacement therapy (ERT) is the current standard of care, which has demonstrated in several studies its efficacy in the prevention and amelioration of progressive and systemic manifestations. Velaglucerase alpha is a glycoprotein with the same amino acid sequence as the human enzyme β-glucocerebrosidase. The aim of this study is to assess the cost-effectiveness of velaglucerase alpha versus imiglucerase for the treatment of type 1 GD from the perspective of the Spanish National Healthcare System (NHS). METHODS: A cost-utility analysis was performed using a semi-Markov model that embedded one decision tree for the initial treatment during two years and a Markov health state structure after the response to the second year receiving ERT, from the NHS perspective. The Markov framework was structured around six health states: asymptomatic, mild, moderate, severe, splenectomy and death and used annual cycles with a time horizon of 39 years. Model structure was validated by a panel of GD experts. Efficacy data were obtained from the HGT-GCB-039 study. Resources consumption was based on expert opinion. Outcomes were quality-adjusted life years (QALY) and costs (€ in 2011). Threshold sensitivity analysis was conducted to determine cost-neutrality between strategies.  RESULTS: Both strategies provided a mean gained of 25.55 QALYs. The average cost per patient for velaglucerase alpha was €7,265,332 compared to €7,327,966 for imiglucerase. The difference in costs was mainly due to the difference in administration costs. The threshold sensitivity analysis showed that velaglucerase alpha will reach cost-neutrality even with a higher unit price.   CONCLUSIONS: Velaglucerase alpha is a cost-saving option for the treatment of type 1 GD in the Spanish setting, providing annual savings compared with imiglucerase. (This study was supported by Shire Pharmaceuticals Iberica)