The paper analyses public divination practice in late republican Rome. Divination is conceptualized as a form of social action under conditions of insecurity which utilizes defined social roles for the interpretation and ritual manipulation of standardized signs in order to measure and articulate consensus and dissent. An overview of the techniques present in the 2nd and 1st centuries ВС sketches the characteristic of prodigia, unexpected, often monstrous signs, and auspicia, radically standardized and frequently employed signs. A closer analysis concentrates on auspices conducted by augurs and magistrates. The author follows three lines of interpretation. First, employing models of political science, the author reconstructs the role of auspices, and in particular the announcement of adverse signs (obnuntiatio), in the process of taking decisions under the senatorial regime. Secondly, the frequent disregard of the announcement of adverse signs in the process of law-giving is interpreted within the framework of different kinds of negotiations, again drawing on models of international relationships. Thus, the quotation of prohibiting signs could be regarded as a form of opting out of the decisional process. Finally, particular attention is given to the timing and staging of public phases of divination, relating religious rituals to the mechanisms of political action and control. In conclusion, the author tries to demonstrate the systems of religious symbols to be a means of communication and an integral part of political institutions of the late republic, thus relating concerns of political history and comparative religion.