Abstract: Indirubin is used clinically for the treatment of chronic granulocytic leukemic in China. Our previous paper reported the syntheses of N₁′substituted derivatives of indirubin.In an attempt to study the role of N₁-substitution and connecting position of two indole rings in the antitumor activity, two N₁-substituted and one N₁N₁, -bissubstituted derivatives of indirubin (Ⅰ₁, Ⅰ₂, Ⅰ₃), and six bisindolinones, derivatives of indigo and isoindigotin (Ⅱ_1～3, Ⅲ_1～3) were synthesized.In the. preparation of compounds Ⅰ_1～3 from N-alkyl-O-acetyl indoxyl Ⅳ (R=-CH₃ or -C₂H₅) with isatin or N-methylisatin, the self-condensation of the indoxyl to N-substituted indigo is suppressed by using strong acid, p-toluenesulfonic acid as condensing catalyst. It has been suggested that aminium formation stabilizes the indoxyl compound thus inhibits the self-condensation and facilitates the desired condensation of indoxyl with isatin to give a yield of 60%. Treatment of indigo with equimolecular quantity of sodium hydride, followed by corresponding alkyl halides, gave compounds Ⅱ_1～3. Isoindigotin series compunds Ⅲ_1～3 were obtained by condensation of the oxindole with corresponding N-alkylisatin.The lipid soluble N-ethyl indigo and N-methyl or N-ethyl isoindigotin exhibit inhibitory action on Walker carcinoma 256 against which their parent compounds are inactive. Substitution on N₁-position of indirubin caused loss of activity, but N₁N₁, -dimethylindirubin (Ⅰ₃) exhibits certain anticancer activity.