The VO2+-Vitamin-B6 (HVB6) complexes with the amino acids: glycine (Hgly), α-alanine (Hαala), β-alanine (Hβala), proline (Hpro), serine (Hser), threonine (Hthr), methionine (Hmet), phenylalanine (Hphe), leucine (Hleu), isoleucine (Hile), valine (Hval) and tryptophan (Htrp) were studied and the binary and tertiary stability constants determinedThe potentiometric measurements were gathered using 1.0 mol.dm-3 NaCl at 25 °C as ionic medium.Exptl. data were analyzed using the computational program, LETAGROP, and HYSS was used to obtain the resp. distribution diagrams.