This paper describes experiments carried out to try to explain the degradation phenomenon of superconducting coils.It is established that flux jumps occurring in a low‐field zone cause a sudden decrease in the series current, which in turn causes a disturbance of field throughout the coil and thus probably results in a quench in a high‐field zone.Degradation of short samples is obtained by following a peculiar cycle of magnetization similar to that observed in a coil. An explanation is given to explain the difference of degradation observed between a short sample and a coil.A measurement of the apparent resistance of a superconducting wire under changing field conditions gives an equivalent resistivity of 10−14&OHgr;·cm fordB/dt= 200 G/sec.