Abstract
We explored intraurban mobility of Tijuana, Mexico, injection drug users (IDUs). In 2005, 222 IDUs underwent behavioral surveys and infectious disease testing. Participants resided in 58 neighborhoods, but regularly injected in 30. From logistic regression, "mobile" IDUs (injecting ≥3 km from their residence) were more likely to cross the Mexico/U.S. border, share needles, and get arrested for carrying syringes-but less likely to identify hepatitis as an injection risk. Mobile participants lived in neighborhoods with less drug activity, treatment centers, or migrants, but higher marriage and home ownership rates. Mobile IDUs should be targeted for outreach and further investigation. The study's limitations are noted.