Objective To examine the prevalence and correlates for needle-sharing among new and long-term injection drug users (IDUs) in Sichuan province, China. Methods Three consecutive cross-sectional surveys were conducted in 6 prefectures of Sichuan province, from 2003 to 2005.Questionnaire-based interviews provided information including socio-demographics, drug-use, sexual behaviors, and HIV-related services. Multivariable logistic regression methodology was used for data analysis. Results Of 3852 eligible participants, the rates of needle-sharing in the last 6 months for IDUs with a less than one year, one to three year, and more than three year injection history were 19.9%,29.1%, and 36.3%, respectively. Needle-sharing for IDUs with a less than one-year injection history was independently associated with factors as: being female, having minority background, higher frequency of injection, sharing injecting equipments, ever having had a non-regular sex partner, or a regular sex partner who injected drugs, never had a test on HIV, being recruited in 2005, and from Zigong prefectm'es of Sichuan. Needle-sharing for IDUs with a 1-3 year injection history were independently associated with receiving less education, having higher frequency of injecting behavior, sharing injecting equipments,ever having had a non-regular sex partner/a regular sex partner who injected drugs, ever having had unprotected sex with a non-regular sex partner, ever having had unprotected sex with a commercial sex partner or client, never attended skill training for HIV/STD prevention, being recruited in 2005 and 2004,and being recruited from Deyang, Zigong, and Liangshan prefectures. Needle-sharing for IDUs with a more than three-year injection history was independently associated with factors as: less education, higher frequency of injecting, sharing injecting equipment, ever had a non-regular sex partner, ever had unprotected sex with a non-regular sex partner, ever had unprotected sex with a commercial sex partner or client, having had regular sex partners who inject drugs, never attended needle exchange programs, being recruited in 2005 and 2004, and being recruited from Deyang, Zigong, and Liangshan prefectures. Conclusion The rates for both needle/paraphernalia sharing and unprotected sex behaviors were high in the IDUs in Sichuan province. These rates were higher among longer-term IDUs than in new IDUs. Our data underlined that better targeted, in-depth and sustained comprehensive intervention packages which including needle exchange, condom promotion along with distribution, and education, were urgently needed to reduce both IDU-related and sex-related risk behaviors among both new and longer term IDUs.