For different chronic applications of array electrodes it is necessary to examine the reaction of the tissue to such electrodes. The present work studied the reaction caused in muscle tissue of rats by implantation of intramuscular multichannel EMG electrodes. Twenty rats were investigated, for periods of 3 till 120 days postoperative. Each animal received two array electrodes (2x8 channels). One electrode was implanted in the c. longum, the other in the c. laterale of triceps muscle. The electrodes have had full silicon coated platinum wires or none coated wires. We developed these flexible and atraumatic electrode arrays to protect the delicate muscle structures. In no case the histological examination revealed a fibrous capsule or inflammation reactions surrounding the electrodes. Additionally no signs of corrosion were present under the microscope on thin platinum plates. The advantage of these electrodes is that they have a high degree of flexibility. Hence there was no tissue inflammation or scarred tissue as a result of intramuscular electrode movement. A current problem is the brittleness of wires. During permanent limb movements the wires accumulates cracks. To resolve this problem we used different kinds of wire modifications. Supported by BMBF (No.: 01EZ0335).