According to theorists of deliberative democracy, deliberation aims at achieving consensus over controversial issues through citizens' debate. Despite the fact that the use of deliberative mechanisms has increased, many commentators have noted a dearth of systematic research on deliberative processes. This paper contributes to this emerging field of research by reporting the results of an analysis of a Citizens' Jury held in Bologna in March 2006. The research results reported here focus on two key themes: (i) selection biases in the Jury selection process and, (ii) evidence of a "treatment effect" following participation in the Jury event. The results from the Bologna Jury experiment reveal that selection bias in citizen juries can be overcome through use of standard procedures, but the effects of citizens' deliberation are likely to be evident only in a limited number of situations.