The cylindrical antenna is potentially useful as a probe for studying the properties of any material in which it is immersed. Examples of possible media are the earth, plasmas, and organic tissues. Such applications presuppose a knowledge of the detailed behavior of the currents and charges along an antenna in a medium with very general properties. In this paper the integral equation for the current along a highly conducting center‐driven cylinder of length 2hand radiusawhen immersed in a homogeneous isotropic medium is solved analytically and simple, and quite accurate formulas are obtained for the distribution of current, the distribution of charge, and the admittance. The lengths 2hmay range from zero to over a wavelength; the radiusais assumed to satisfy the conditiona≪h. The real effective conductivity of the medium may extend from zero to arbitrarily large values, the real effective permittivity from large negative values (as in certain plasmas) to large positive values (as in ordinary dielectrics like water).