Latvia, a country with levels of multidrug-resistant (MDR) TB among the highest in the world, experienced a 58-fold increase in HIV seroprevalence among all persons tested in the country from 1996 through 2001. In addition, HIV seroprevalence among TB cases increased from 0.4% to 1.4%, and among MDR-TB cases from 0% to 5.6% from 1998 through 2001, potentially compromising gains made to date in controlling the country's MDR-TB epidemic. The following will be critical to the future of MDR-TB control in Latvia: containing HIV transmission in the country, particularly among injection drug users who comprised 72% of all HIV cases reported in the country by the end of 2001, as well as 81% of all MDR-TB cases co-infected with HIV; expanding capabilities to more rapidly detect and successfully treat patients with MDR-TB; developing mutual TB control strategies between the National TB and AIDS programs; and continuing to improve institutional infection control measures, particularly in hospitals and prisons where an increasing number of persons infected with HIV come into contact with persons with active MDR-TB.