This paper presents an efficient method to synthesize cascaded sigma-delta modulators implemented with continuous-time circuits. It is based on the direct synthesis of the whole cascaded architecture in the continuous-time domain instead of using a discrete-to-continuous time transformation as has been done in previous approaches. In addition to place the zeroes of the loop filter in an optimum way, the proposed methodology leads to more efficient architectures in terms of circuitry complexity, power consumption and robustness with respect to circuit non-idealities.This work has been supported by the Spanish Ministry of Science and Education (with support from the European Regional Development Fund) under contract TEC2004-01752/MIC.Peer reviewed