The read/write heads in flexible disk drives operate in the presence of AC and DC magnetic fields generated by solenoids, motors, recording head erase structures, circuit board components, and external sources such as CRT flyback transformers present in "smart terminals and word processors. Time varying magnetic fields induce signal on the read/write coil and introduce interference. This interfering signal increases the error rate and can cause "extra bits". Steady state fields cause shifts in the location of transitions, which also translates into higher error rates. The benefits derived from various shield configurations in and external to the flexible disk drive are presented.