['To review the legal and regulatory barriers that restrict pharmacy sales of syringes to injection drug users (IDUs) and to discuss how reducing these barriers can facilitate access to sterile syringes for IDUs and improve HIV prevention.', "IDUs' access to sterile syringes from community pharmacies in the United States is limited by state laws and regulations governing syringe sales. Restricted availability of sterile syringes from pharmacies is a structural barrier that greatly impedes HIV prevention for IDUs, who often share and reuse syringes because they cannot obtain and possess sterile syringes. These high-risk behaviors contribute to the transmission of HIV and other blood-borne pathogens among IDUs, their sexual partners, and their children. STATE EXPERIENCES: In Connecticut, because of high HIV prevalence among IDUs, restrictive syringe laws were changed. After the legal changes in Connecticut, both pharmacy sales of syringes in areas of high drug use and purchases of syringes in pharmacies (reported by IDUs) increased, while syringe sharing (reported by IDUs) decreased. Maine and Minnesota have made similar changes in laws."] Are syringe laws and pharmacy regulations structural constraints on HIV prevention in the US?