Abstract: The compound, α-keto-β-ethoxybutyraldehyde bisthiosemicarbazone (Ⅰ), reported in our previous paper showed marked carcinostatic activity against several animal tumors and has been used in clinical trial. Because of its poor water solubility and absorption from the gestrointestinal tract, twenty-nine compounds related to (Ⅰ) have been prepared by direct condensation of the appropriate α-ketoaldehyde (Ⅱ, R-CH₃, C₂H₅, n-C₃H₇, n-C₄H₉) with different amino compounds in order to search for antitumor and antiviral agents with lower toxicity and better water solubility as well as to explore structureactivity relationship. The compounds prepared are listed in table Ⅰ.The screening data showed that the antitumor activity of the condensation products of α-keto-β-alkoxy-butyraldehyde varied with different amino moieties. The α-keto-β-alkoxy-butyraldehyde bis-thiosemicarbazones (1-3) showed the highest inhibitory action, while substitutions in the N⁴ position either reduced (N⁴-methyl 4,5) or abolished (Naryl, 6-9, N-p-bromophenyl, 10-11) the activity. Replacement of the sulphur atom in the thiosemicarbazone with oxygen (13-16), imino group (17) or methylthio group (18-19) also decreased the efficacy. Compound (12) inhibited the growth of chlamydozoa trachomatis at a minimun concentration of 5μg/ml. None of the compounds exhibited any activity against influenza virus (PR-8 strain).