There is considerable evidence that drug injectors are reducing their HIV risk, but changes in syringe sharing behaviour have been greater than those in sexual risk behaviour. This paper reviews the literature on sexual risk behaviour in injecting drug users. It focuses on the major areas of concern: HIV prevalence among drug injectors; sexual risk behaviour; the potential for heterosexual transmission; condom use; sexual risk and women; pregnancy; male homosexual activity and drug use; the effect of drugs on sexual behaviour and prostitution. The paper also considers some of the difficulties in changing sexual risk behaviour and suggests some ways forward for intervention and prevention.