Many of the specific factors and causes found to be responsible for signal dropout occurring on instrumentation magnetic tape are described. Dropout producing substance are identified through optical and microchemical techniques; these findings are correlated with measured electrical signal losses to provide source identification of foreign substance present. Instrumentation used to evaluate tape condition and provide real-time monitoring in the field is also described. Effective procedures are outlined for achieving significant improvement in tape life and reducing overall operating costs for the magnetic recording systems which utilize these tapes.