Copper(ll) complexes of 6-methyl-2-formylpyridine thiosemicarbazone, and its *N-methyl-, *N-ethyl-, 4N-phenyl-, 4N-dimethyl-, 4N-diethyl-, 4N-dipropyl-, 3-pyrrolidinyl, 3-piperidinyl-and 3-hexamethyleneiminylthiosemicarbazone derivatives were prepared and characterized. I.r., electronic and e.s.r, spectra of the complexes, as well as ~H and ~ 3C n.m.r, spectra of the thiosemiearbazones, were obtained. The thiosemicarbazones and their eopper(II) complexes show either modest or no growth inhibitory activity against Aspergillus niger, but the *N-dialkyl-and 3-azaeyclo-derivatives exhibit considerable activity against Paecilomyces variotii.