The determination of the resistance of plane dissipative layers by impedance measurement is treated. Special attention is devoted to the range 1–104Ω per square at 7Gc/s. Formulas are derived from transmission-line theory by making certain approximations, and the ranges of validity of these approximations are discussed. For 10–300Ω per square, a simple graphical method is given. Experimental results show that the h.f. and d.c. resistances for two kinds of layers agree, but that a third kind shows substantial differences between the two resistances.In an Appendix a formulation of the input impedance of transmission lines is proposed that is specially suitable for transmission lines consisting of sections with different propagation coefficients.