Multidrug resistant tuberculosis (MDR-TB) is a serious, feared, and difficult to control problem, and is showing a growing tendency worldwide. Objective: To make a risk factors analysis for acquired MDR-TB. Methods: A population-based case-control study was conducted in a retrospective way. Multidrug resistance was defined as resistance to at least Rifampin (RFM) + Isoniazid (INH), and susceptible TB was defined as the case that had had the first treatment in a period similar to the first treatment of the MDR-TB cases, but that was cured at the moment of the interview. The selection of cases was made based on the list of Susceptibility Tests (ST) carried out at the Central Laboratory of Public Health of the State of Ceará, in the period 1990 to 1999. The Proportion Method was used to make a survey of resistance to the six antituberculosis drugs (isoniazid, rifampin, pyrazinamide, ethambutol, ethionamide, streptomycin) that represent the standard treatment in Brazil. Controls were selected from the book of registry of TB cases. Univariate and multivariate analysis was performed and statistical significance was considered with a p value < 0.05. Results: Of the 1,500 ST performed in the period, 266 strains were multidrug resistant. Only 153 patients were identified. Of these, 19 were excluded. The Group of Cases comprised 134 patients and the Controls, 185. The following risk factors were found after the multivariate analysis: lack of sewer in the domicile, alcoholism + tobacco smoking, number of previous treatments, irregular treatments and lung cavities. Conclusion: Based on the evidence, conclusion is that these five factors play a role in the development of acquired MDR-TB, and that neutralizing such factors can contribute to the control of tuberculosis.