Carbon-13 n.m.r. spectra are reported as a function of pH for mixtures of dipropylenetriamine (dpt) or N-(2-aminoethyl)propane-1,3-diamine (aepn) and zinc nitrate, of zinc and dpt or aepn with 1,2-diaminoethane (en), 1,3-diaminopropane (pn), and glycine (gly), and of zinc and aepn with L-alanine (ala), β-alanine (β-ala), and trans-1,2-diaminocyclohexane (dach). Carbon-13 chemical shifts are also reported as a function of pH for dpt, β-ala, and dach alone. The pH profiles have been analysed by computer and chemical shifts determined for the following species: dpt, Hdpt⁺, H₂dpt²⁺, H₃dpt³⁺, β-alaO, β-ala, dach, Hdach⁺, H₂dach²⁺, [Zn(dpt)]²⁺, [Zn(dpt)(Hdpt)]³⁺, [Zn(dpt)₂]²⁺, [Zn(dpt)(OH)]⁺, [Zn(dpt)(en)]²⁺, [Zn(dpt)(glyO)]⁺, [Zn(aepn)]²⁺, [Zn(aepn)(Haepn)]³⁺, [Zn(aepn)₂]²⁺, [Zn(aepn)(OH)]⁺, [Zn(aepn)(en)]²⁺, [Zn(aepn)(pn)]²⁺, [Zn(aepn)(dach)]²⁺, [Zn(aepn)(glyO)]⁺, [Zn(aepn)(alaO)]⁺, and [Zn(aepn)(β-alaO)]⁺. Stability constants have also been determined for the bis and ternary complexes. Potentiometric titrations with dpt, zinc + dpt, and zinc + aepn solutions provide support for the interpretation of the chemical shift data. The results are compared with those of a previous study with diethylenetriamine and used to provide evidence concerning the co-ordination geometry of zinc in these complexes.