The use of illicit drugs plays a critical role in the spread of HIV, with approximately one-half of all new HIV infections in the United States attributed to this mode of transmission. There is a renewed emphasis on developing special HIV counseling and testing (C&T) programs for drug users. We conducted a qualitative study of C&T providers to identify client-centered and structural barriers to providing HIV C&T to high-risk drug users. Interviews focused on obtaining a detailed description of the services; successful and problematic forms of organization, financing, and service delivery; client access and barriers to C&T services; recommendations for increasing C&T accessibility and utilization by drug users; and linkages between C&T and other HIV-prevention and intervention services. The results of our interviews illustrate that it is tremendously complex and challenging work to provide C&T to populations with multiple and immediate needs within a context of layered constraints on individual behavior, provider resources, and service delivery. Providers clearly understand client-centered and structural barriers and have demonstrated a commitment to overcoming the barriers related to AIDS stigma, confidentiality, material needs, and fear when delivering HIV C&T services.