OBJECTIVES: Systemic administration of anti-TNF alpha leads to an anti-inflammatory and joint protective effect in pathologies such as rheumatoid arthritis, psoriasis, Crohn’s disease. The aim of this study was to assess adherence to therapy and stay on treatment (no switches or interruptions) of patients treated with biologics according to therapeutic indication and to calculate healthcare resources consumption (drugs, outpatient services, hospitalizations). METHODS: An observational retrospective cohort analysis based on 5 Local Health Units administrative databases was conducted. Patients who filled at least one prescription for anti-TNF alpha between 01/01/2009-31/12/2011 were included. Patients were followed-up for one year. Patients were defined as adherent if they had >80% of follow up period covered by drugs dispensation. RESULTS: A total of 1,219 patients were analyzed, 47% male, age 49.6±14.6. Patients affected by rheumatoid arthritis were 36%, psoriasis 31%, Crohn’s disease 10%, psoriatic arthritis 7%, ulcerative colitis 3%, ankylosing spondylitis 3%, diagnosis not available 11%; 420 (34%) were treated with Adalimumab, 615 (50%) Etanercept, 184 (15%) Infliximab. Among the 94% of patients who did not switch, patients treated with Infliximab seemed to have the highest rate of adherent patients across all indications: 51%, VS 27% Etanercept and 23% Adalimumab; at the multivariable logistic regression model, Infliximab resulted a protective predictor of non adherence for all indications (OR ranged from 0.08 to 0.43). For patients who started a first-line biological drug, stay on treatment was 73% for Infliximab, 67% Etanercept, 64% Adalimumab. The mean annual expenditure for each patient in analysis was €11,120; in particular, non-pharmacological expenditure was €988 for adherent and €1,255 for non-adherent patients; at the multivariable generalized linear model, Infliximab was associated with the lowest cost for all indications. CONCLUSIONS: Patients treated with Infliximab were associated to higher adherence and stay on treatment and lower costs, as compared to Adalimumab and Etanercept.