A series of organotin complexes with pyrrole-2-carboxaldehyde 2-hydroxybenzoylhydrazone (H3mfps) and pyrrole-2-carboxaldehyde 2-picolinoylhydrazone (H2mfpp) was investigated. The IR, 1H, and 119Sn nuclear magnetic resonance spectroscopic characterization of all the compounds is reported and discussed in connection with the ligand behaviour of the hydrazone and the structure of the organotin complex. Complexes exhibit antibacterial properties higher than those of the corresponding ligands but they turn out to be less potent than the parent organotin compounds. Sn(H3mfps) (C6H5)2Cl2.2H2O and Sn(Hmfpp)(n-C4H9)2Cl are the most active antibacterial compounds showing MIC values between 3-6 micrograms/ml against Bacillus subtilis and Staphylococcus aureus and between 6-25 micrograms/ml against Escherichia coli; the first compound also strongly inhibits the growth of Aspergillus niger. All the ligands and complexes are devoid of DNA-damaging activity in the Bacillus subtilis rec-assay. H2mfpp and its complexes Sn(Hmfpp)(C2H5)2Cl and Sn3(Hmfpp)(mfpp) (C6H5)3Cl6 are shown by the Salmonella-microsome assay to be mutagenic substances in the presence of a metabolic activation system. The obtained results are discussed on the basis of structure-activity relationships.