The complexation equilibria of zinc(lI) with 2-hydroxy-1,4-naphthoquinone, 5-hydroxy- 1,4-naphthoquinone and 5.8-dihydroxy- 1,4-naphthoquinone have been studied spectrophotometrically as a function of pH in 50% (v/v) ethanol-water medium at 25°C and an ionic strength of 0.1M NaClO4. The spectral study of the complexation reactions has been carried out in solutions containing equimolar concentrations or an excess of one component in the pH range of study. The chelation capabilities of these hydroxynaphthoquinones with zinc(II) have been examined. The complexation equilibria have been demonstrated and characterized by analysis of the absorbance versus pH graphs. The composition, molar absorptivities, equilibrium constants and stability constants of zinc(II) complexes with these reagents have been determined. The fundamental conditions favouring direct spectrophotometric determination of trace amounts of zinc(II) using naphthazarin have been investigated.