We conducted a qualitative study to examine the impact of an HIV prevention programme on female sex workers' lives in Guntur district, Andhra Pradesh. The study found evidence that, in addition to the HIV prevention programme, structural and environmental factors had recently changed the way sex work was being practiced. Recent closure of the brothels and implementation of a late-night street curfew by the police meant sex work had become more hidden, with clients often solicited using mobile phones from home or their work place (e.g., in the fields or factories). Sex work had become safer, with violence by non-regular partners rarely reported. Women understood the risks of unprotected vaginal sex and reported using condoms with their clients. However, clients were more frequently requesting anal sex, possibly due to recent exposure to pornography following increased accessibility to modern technologies such as mobile phones and the Internet. Anal sex with clients was common but women were often unaware of the associated risks and reported unprotected anal sex. HIV positive and/or older women faced severe financial hardship and difficulty soliciting sufficient clients, and reported unprotected vaginal and anal sex to earn enough to survive. Taken together, the findings from this study suggest changing vulnerability to HIV in this setting. It will be important for HIV prevention programmes to be flexible and creative in their approaches if they are to continue to reach this target community effectively.