Twenty-three arylthioureines bearing β-alanine or γ-aminobutyric alkyl ester chains were synthesized for in vitro screening toward 44 strains of fungi and 2 genera of nematodes. The nitro derivatives were the most potent compounds againstAspergillus and Candida strains. Ester chains increase activity against the filarial worm Molinema dessetae. Twelve compounds have EC 5 0 < 40 μg/ml. However, the anthelmintic potency is weak compared with tetramisole.