As a means of utilizing 3, 3′-dihydroxydiphenylamine in the distillation residue of m-aminophenol, the amine or its methylated 3, 3′-dimethoxydiphenylamine was derived to 2, 8-dihydroxyphenothiazine or 2, 8-dimethoxyphenothiazine by fusion reaction with sulfur and anthelmintic action of these compounds was compared with that of phenothiazine and piperazine phosphate. 2, 8-Dihydroxyphenothiazine was so unstable that it was derived to its triacetate. The amino group in these diphenylamines was reacted with alkylaminoalkyl chloride with sodium amide or sodium hydride as the dehydrochlorination agent and 3, 3′-dimethoxydiphenylamine and 2, 8-dimethoxyphenothiazine, substituted with diethylaminoethyl, dimethylaminoethyl, diethylaminopropyl, and 1-methyl-3-piperidylmethyl groups were prepared. Antihistamine action of these derivatives was compared with that of chlorpromazine and Anergen.