Efficacy has been a long standing topic in research on risk communication. Academic experts have been persistent in offering advice and recommendations to practitioners in industry and government. Still there is evidence that practitioners are not up to date on these advices. Characteristically advice is formulated from an outside view on practice without taking into account practitioners own understandings and the organizational conditions for their work. This study adopts a bottom up approach to the efficacy of risk communication. It draws on interviews with practitioners at six government agencies in Sweden who do risk communication as part of their work. The agencies are responsible for the policy areas of food, chemicals, environmental protection, housing and building, traffic, and contingency planning and management. The interviews focused on what lessons the practitioners thought they had learnt from successful and failed cases of risk communication. A number of factors for success and failure as understood by the practitioners themselves have been identified. Some factors explain both success and failure while some predominantly explain either failure or success. There is a tendency that failure is attributed to external circumstances such as the difficulty of the task (to handle the media or deal with public ignorance or lack of knowledge) while success is explained by internal elements such as competence, dedication and persistence to solve the task. The factors for effectiveness are discussed in relation to the academic recommendations on risk communication. It is concluded that if academic advice on risk communication is going to reach out to practice, advice needs to take into account practitioners’ knowledge and experiences of effective risk communication.