This paper assesses the reasons for entry into sex work and its association with HIV risk behaviours among mobile female sex workers (FSWs) in India. Data were collected from a cross-sectional survey conducted in 22 districts across four high HIV prevalence states in India during 2007-2008. Analyses were limited to 5498 eligible mobile FSWs. The reasons given by FSWs for entering sex work and associations with socio-demographic characteristics were assessed. Reported reasons for entering sex work include poor or deprived economic conditions; negative social circumstances in life; own choice; force by an external person; and family tradition. The results from multivariate analyses indicate that those FSWs who entered sex work due to poor economic conditions or negative social circumstances in life or force demonstrated elevated levels of current inconsistent condom use as well as in the past in comparison with those FSWs who reported entering sex work by choice or family tradition. This finding indicates the need for a careful assessment of the pre-entry contexts among HIV prevention interventions since these factors may continue to hinder the effectiveness of efforts to reduce the spread of HIV/AIDS in India and elsewhere.