Thirty-four thiosemicarbazones and S-alkyl thiosemicarbazones, and some of their Zn-II and PDII complexes were obtained and purified to investigate antimicrobial activity. MIC values of the compounds,A ere deter mined by the disc diffusion method against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, Stophylococcus aureus, S. epidermidis, and Candida albicans. The thiosemicarbazones show antibacterial and antifungal effects in free ligand and metal-complex form. Picolinaldehyde-S-methyl- and -S-benzylthiosemicarbazones did not affect the tested microorganisms but their Zn-II complexes showed selective activity. The antimicrobial activity is relatively high in Me2SO, but the antimicrobial potential is changed in a certain range with Me,SO, HCONMe2, EtOH and CHCI3.