In wireless sensor networks, compromised sensor nodes aim to distort the integrity of data by sending false data reports, injecting false data during data aggregation, and disrupting transmission of aggregated data. Previously known trust systems rely on general reputation concept to prevent these attacks. However, this paper presents a novel reliable data aggregation and transmission protocol, called RDAT, which is based on the concept of functional reputation. Protocol RDAT improves the reliability of data aggregation and transmission by evaluating each type of sensor node action using a respective functional reputation. In addition, protocol RDAT employs a fault tolerant Reed-Solomon coding scheme based multi path data transmission algorithm to ensure the reliable data transmission to the base station. The Simulation results show that protocol RDAT significantly improves the reliability of the data aggregation and transmission in the presence of compromised nodes. (C) 2008 Elsevier B.V. All rights reserved.