Interstim® therapy has shown a higher effectiveness and safety compared to surgical procedures like dynamic graciloplasty or artificial anal sphincter in patients with intact anal sphincter (IAS) and before Sphincteroplasty in patients with structural deficient anal sphincter (SDAS), a condition with a high impact on psychological and social life in healthy people. OBJECTIVE: To assess the cost-effectiveness of two FI management scenarios, with and without SNS, and to estimate the potential budget impact of its progressive introduction in the Spanish setting. METHODS: A decision analytic model was developed, representing the possible clinical paths for each of the scenarios (with and without SNS), as well as its clinical and economical consequences in mid-long term with a Markov model. Clinical and resource use data were retrieved from literature and validated by a clinician expert's panel. Efffectiveness was measured with both QALYs and symptom free years (SFY). A 3% discount rate was used for future costs and benefits (time horizon= 5 years). Prevalence figures where combined with Interstim sales forecasts to estimate the total number of patients to receive therapy the next years and the associated budget impact. RESULTS: The introduction of Interstim® in the therapeutic management of FI has an associated cost-effectiveness of 22,910€ (IAS patients) and 22,546€ (SDAS patients) per QALY gained. The progressive introduction of Interstim® in 150 to 250 patients/year will have an estimated budget impact of 320,049€, 490,550€ and 667,824€ for next three years (net increase of 0.3% to 0.5% of total costs in patients with IF). CONCLUSIONS: Introducing Interstim® in the management of FI in IAS and SDAS patients in the Spanish setting, has shown to be an efficient measure with a C/E rate below the accepted Spanish threshold (30,000€/QALY), and with a relatively low additional cost for the Spanish NHS.