We report the results of magnetic [electron-spin resonance (ESR) and susceptibility];ana conductivity measurements on a new type of semiconducting polymer : poly(vinylene disulfide)-(S CH=CH-S)(n) synthesized;from (E)-1,2 dithiocyanatoethene. ESR spectra of pristine and protonic acid doped samples have four g factor values which can be explained by the nonplanar structure of the polymer. Decrease in paramagnetism and enhancement of the spin density by doping are observed to be in close relation with the increase of the conductivity. A conduction mechanism assuming direct protonation of the polymer backbone is proposed to explain the behavior of these polymers upon chemical doping by protonic acid.