This report summarizes current (as of 2011) guidelines or recommendations published by multiple agencies of the U.S. Department of Health and Human Services (DHHS) for prevention and control of human immunodeficiency virus (HIV) infection, viral hepatitis, sexually transmitted diseases (STDs), and tuberculosis (TB) for persons who use drugs illicitly. It also summarizes existing evidence of effectiveness for practices to support delivery of integrated prevention services. Implementing integrated services for prevention of HIV infection, viral hepatitis, STDs, and TB is intended to provide persons who use drugs illicitly with increased access to services, to improve timeliness of service delivery, and to increase effectiveness of efforts to prevent infectious diseases that share common risk factors, behaviors, and social determinants. This guidance is intended for use by decision makers (e.g., local and federal agencies and leaders and managers of prevention and treatment services), health-care providers, social service providers, and prevention and treatment support groups. Consolidated guidance can strengthen efforts of health-care providers and public health providers to prevent and treat infectious diseases and substance use and mental disorders, use resources efficiently, and improve health-care services and outcomes in persons who use drugs illicitly. An integrated approach to service delivery for persons who use drugs incorporates recommended science-based public health strategies, including 1) prevention and treatment of substance use and mental disorders; 2) outreach programs; 3) risk assessment for illicit use of drugs; 4) risk assessment for infectious diseases; 5) screening, diagnosis, and counseling for infectious diseases; 6) vaccination; 7) prevention of mother-to-child transmission of infectious diseases; 8) interventions for reduction of risk behaviors; 9) partner services and contact follow-up; 10) referrals and linkage to care; 11) medical treatment for infectious diseases; and 12) delivery of integrated prevention services. These strategies are science-based, public health strategies to prevent and treat infectious diseases, substance use disorders, and mental disorders. Treatment of infectious diseases and treatment of substance use and mental disorders contribute to prevention of transmission of infectious diseases. Integrating prevention services can increase access to and timeliness of prevention and treatment.