OBJECTIVES: Present a systematic review of efficacy, effectiveness and safety of pharmacological treatments (sibutramine and orlistat) used in obesity treatment and performs a cost-effectiveness analysis comparing: (a) Diet; (b) diet plus sibutramine and (c) diet plus orlistat under the public health system perspective. METHODS: A systematic review of literature produced the estimates of co-morbidities risks and disease progression with and without the interventions. A Markov model that simulates related obesity comorbidities as chronicle heart disease and diabetes mellitus was build.  Discount rate assumed was 5% and the outcome data was taken from international literature and was measured by QALY.  Direct cost was calculated by the authors using data from public health system databases, as well as in related cost studies made in Brazil.  PARTIAL RESULTS: The systematic review has initially provided results of effectiveness of the interventions. Weight loss values after one year of treatment ranged from -6,35 kg to sibutramine 15mg and -2,89kg to standard care (only Diet). All patient gain weight after intervention in a rate of 0,385kg/month (first four years), and at 1kg/year in the next years. Annual costs of co-morbidities were estimated in U$7,017.00 to infarction and U$1,335.00 to diabetes. CONCLUSIONS: More data will be collected, to complement this preliminary serving as input to complete de cost-effectiveness model.