Many coordination complexes of iron(II) oxalate, cobalt(II) oxalate, copper(II) oxalate, cobalt tetrathiocyanatomercurate(II), copper tetrathiocyanatomercurate(II) and iron tetrathiocyanatomercurate(II) with various aliphatic, aromatic, and heterocyclic amines have been synthesized and tested for their toxicity on mice, amoebicidal activity against E. histolytica and antibacterial activity against S. aureus. Three complexes CoC2O4 (orthophenylenediamine)2, Cu[Hg(SCN)4] (ethylenediamine)2 and Cu[Hg(SCN)4] (propylene diamine)2 exhibited pronounced antiamoebic activity whereas all thiocyanate complexes and CoC2O4 (ethylenediamine)2 showed significant antibacterial action against S. aureus. Possible structure-activity relationship has been postulated, and it has been noticed that toxicity and the amoebicidal and bactericidal activities of the metal complexes increased with a decrease in the ionic radius of the metal ion.