A unified theoretical concept for noise analysis in analog and microwave circuits is introduced. Based on the adjoint system approach an analysis technique for general-purpose CAD (computer-aided design) applications is presented. The algorithm is easy to implement into existing CAD tools, and exploits the advantages of sparse matrix techniques. As an example, in a linear SPICE-analysis of an amplifier, only an additional forward and backward substitution for each port, two 2*2 matrix multiplications for each transistor, and the outer product of two two-dimensional vectors for a resistor are needed. >