This paper analyses the redistributive and efficiency effects of extending at national level the Reddito minimo di inserimento, introduced experimentally in 1998 in some Italian municipalities. We develop a behavioural micro-simulation tax-benefit model that allows for simultaneous labour supply decisions by household members, endogenous choice between dependent employment and self-employment, complete representation of the current Italian tax-benefit system. The results show a positive impact on both inequality and poverty, while overall labour supply would reduce. On average magnitude of labour supply disincentive would be small for married individuals, relatively larger for single persons and, within this category, for women than men.