It is well known that the small‐signal behavior of long electron beams may be analyzed in terms of propagating space‐charge waves, suggesting an equivalence between such beams and longitudinally moving transmission lines. This in turn suggests the analysis of such electronic devices as the traveling‐wave amplifier, double‐stream or electron‐wave amplifier, and multicavity magnetron, in terms of coupled distributed‐parameter transmission lines moving relative to each other. It is shown that this approach is equivalent to a rigorous field‐theory analysis in certain cases of particular interest, and the procedure for calculating the significant distributed parameters is indicated. Final results for the idealized helix and thin cylindrical electron beam are presented.