A fast and efficient synthesis of some 1,4-disubstituted thiosemicarbazide derivatives is described. The reaction of 3-chlorobenzoic acid hydrazide with various aryl isothiocyanates gave thiosemicarbazide derivatives (1-11) in good yield. The cyclization of compounds (1-11) in the presence of 2% NaOH resulted in the formation of compounds (12-22) containing the 1,2,4-triazole ring. A series of new Mannich bases (23-33) related to the structure of 1,2,4-triazole has been also synthesized. All of these compounds were tested for their in vitro antibacterial activity against the reference strains of aerobic bacteria - 6 Gram-positive and 3 Gram-negative ones; 12 Staphylococcus aureus clinical isolates were also examined. An attempt was made to clarify the influence of the nature/position of substituents on antibacterial activity of compounds described.