A systematic dielectric study over a frequency range from 400 to 10 MHz was carried out on natural rubber and chloroprene rubber with a small amount of nitroaniline additives. Three absorption regions were obtained as a result of the analysis of the curves relating dielectric loss epsilon " with frequency. The first absorption region in the lower-frequency range could be attributed to the Maxwell-Wagner effect. The second absorption region which could be attributed to the ingredients added to rubber was found to be nearly the same for doped and undoped natural rubber samples, while it decreases by the addition of aniline derivatives to chloroprene rubber samples. The third region which is associated with Debye losses is found to be also nearly the same for natural rubber samples, while it decreases by the addition of aniline derivatives to chloroprene rubber; this decrease is interpreted according to the peptizing effect of aniline derivatives. For the expired chloroprene rubber gum, aniline derivatives were added and the mechanical and electrical behavior was improved to approach the unexpired one.