Electric field distribution in biological systems was investigated. In the analysis both the conductive and the dielectric properties of biological systems were considered. Making use of the complex dielectric coefficient, equations which describe the electric field behavior in such media, were formulated. These equations were solved numerically for a few biological systems. The solutions show that the macroscopic field distribution, for example, the refraction of the ECG wave upon passing from one tissue into another, is mainly determined by the tissue's conductive properties (in the frequency range of 0–108 Hz). However, the microscopic field distribution around the individual cells is determined by the conductive, the dielectric or both properties, depending on the frequency. At frequencies below 104 Hz the field configuration is determined largely by the system's conductive properties. At frequencies above 107 – 108 Hz, by the dielectric properties and in the range of 104 – 106 Hz both properties affect the field distribution. In this range the field direction may be shifted by as much as 90° by relatively small frequency changes.