Tuberculosis is still considered to be a threat to public health in the Netherlands. The Dutch Public Health Act enables the mandatory isolation of contagious patients who are not willing to be treated. However, this act does not mean that patients can be treated against their will. Another act, the Dutch Medical Treatment Act, regulates the contract between doctor and patient. According to this act, only patients who are mentally incompetent can be treated against their will. We describe two patients with contagious tuberculosis who are mentally incompetent. This article explains the steps which, in accordance with both acts, must be followed before starting appropriate treatment