This paper evaluates the role of female sex worker (FSW) collectives in the state of Karnataka, India, regarding their facilitating effect in increasing knowledge and promoting change towards safer sexual behaviour. In 2002 a state-wide survey of FSWs was administered to a stratified sample of 1,512 women. Following the survey, a collectivization index was developed to measure the degree of involvement of FSWs in collective-related activities. The results indicate that a higher degree of collectivization was associated with increased knowledge and higher reported condom use. Reported condom use was higher with commercial clients than with regular partners or husbands among all women and a gradient was observed in most outcome variables between women with low, medium and high collectivization index scores. Collectivization seems to have a positive impact in increasing knowledge and in empowering FSWs in Karnataka to adopt safer sex practices, particularly with commercial clients. While these results are encouraging, they may be confounded by social desirability, selection and other biases. More longitudinal and qualitative studies are required to better understand the nature of sex worker collectives and the benefits that they can provide.