Over the past 6 to 7 years an increasing incidence of acute hepatitis C virus (AHCV) has been fuelled by two different changing epidemics: (1) a new resurgence of AHCV amongst intravenous drug users (IVDU); and (2) presumed sexually transmitted AHCV amongst predominantly HIV-positive men who have sex with men (MSM). Increasing incidence amongst IVDUs is likely to be a consequence of changing injecting behaviour, possibly related to changes in perception of HIV as well as HCV risk and consequences. Increasing incidence amongst MSM is likely to be a consequence of changing sexual practices, for example number of sexual partners and type of sexual behaviour, as well as increasing availability of recreational drugs associated with sexual risk-taking, and wider availability of casual sexual partners via the internet or sex-on-premises venues. It remains unclear whether the current outbreaks in MSM, predominantly seen in HIV-positive individuals, reflect a predisposition to AHCV secondary to HIV status per se, or whether this reflects differences in behaviour amongst HIV-positive versus HIV-negative MSM, or potentially increased screening (either routine or secondary to abnormal liver function tests) in HIV-positive MSM. The majority of individuals with AHCV are asymptomatic and therefore routine screening of individuals in at-risk groups with abnormal liver function tests should be considered. Previous historical studies suggest that individuals with concomitant HIV infection are far less likely than those without to spontaneously clear HCV. It is currently recommended that such individuals acutely infected with HCV should undergo monitoring of HCV viral load levels to determine whether spontaneous clearance is likely or whether the opportunity for early treatment should be considered.