This paper examines whether female participation in the labour force enhances the autonomy of women in poor populations. The data are from a survey of 529 women in urban slums and rural Scheduled Caste settlements in Tamil Nadu, India. In order to see whether working women play a greater role than non-working women do in household decisions, information on women's role in various social and economic activities was obtained. In most activities, a large proportion of working women have a greater say than non-working women in urban areas, but working women in rural areas do not have such an advantage. Factor analysis was carried out to identify key factors of autonomy. Mean factor scores were significantly higher for poor working women than for non-working women in the urban areas, but not in the rural areas. Results of regression analysis using predicted factor scores showed that in urban areas work participation enhances female autonomy even after controlling for other socio-economic and demographic factors. But this was not true in the case of rural women. Thus, female participation in the labour force seems to act differently on autonomy in urban and rural areas.