Poly(ethyleneimine S-alkyldithiocarbamate)s were prepared from poly(ethyleneimine sodium dithiocarbamate) and alkyl chlorides, aralkyl chlorides, substituted alkyl esters of chloroacetic acid, p-chloroethyl esters of carbamic and carboxylic acids, and N-substituted chlorocarboxamides, respectively. The poly(ethyleneimine) derivatives thus obtained were decomposed physically and chemically to release sulfur and sulfur-containing substances, and acted as controlled-release herbicides or fungicides.