In this paper analysis of interconnected dynamical systems are considered. A solid framework for the analysis of the stability of interconnection is given. The results from Fax and Murray (2002) that studies the SISO-case for a constant interconnection matrix are generalized to the MIMO-case where arbitrary interconnection is allowed. The analysis show existence of a separation principle that is very useful in the sense of the simplicity for stability analysis. Stability could be checked graphically using a Nyquist-like criterion. The problem with time-delays and interconnection variation and robustness appear to be natural special cases of the general framework
