The authors present techniques for the analysis of signal propagation in the interconnections used in VLSI systems. The propagation is modelled by coupled transmission lines which include losses. For conductors whose thickness is small compared to the skin depth over the principal spectrum of the pulse being propagated, the losses can be treated as frequency-independent; otherwise, the losses must be calculated as a function of frequency. It was observed that the inductance may be approximately treated as constant, but the resistance variations in frequency may be significant. A semianalytical method for computing the transients in lossy lines serves as the basis for the simulation of nonuniform lines.