In an effort to develop new organotin materials for investigation and biocidal evaluation, a series of compounds with the general formula R4-nSrLn (where R = CH3, n-C4H9, C6H5, C6H5CH2 and L = 3-(N-naphthylaminocarbonyl)-2-propenoic acid) were synthesised, and characterised by elemental analysis, IR, multinuclear (H-1, C-13 and Sn-119) NMR, Sn-119m Mossbauer spectroscopy and mass spectrometry. The biological activity of these compounds against various bacteria and fungi was investigated. All of the compounds were active against the fungi tested with a few exceptions. These compounds also showed significant antibacterial activity. LD50 data show that the investigated compounds have significant toxicity.