Interaction　between　1-[4-(2-carboxyl-ethyl-)phenoxy]　phthalocyanine　Zinc(II)　(ZnPcC1)　and　albumin　(human　serum　albumin　or　bovine　serum　albumin)　was　studied.　ZnPcC1　can　be　covalently　bound　to　albumin　through　amide　bond　formation.　The　molar　ratios　of　ZnPcC1　to　albumins　are　found　to　be　about　7　:　1　in　the　covalent　bioconjugates.　On　the　other　hand,　there　are　strong　non-covalent　interactions　between　ZnPcC1　and　albumins　with　a　binding　constant　of　ca.　1.　0　X　10(5)　mol(-1).L.　Binding　sites　competition　experiments　suggest　that　the　binding　site　locates　in　subdomain　I　B　of　human　serum　albumin.　When　conjugated　to　albumin,　no　matter　covalent　conjugation　or　non-covalent　conjugation,　the　ZnPcC1　exhibit　more　distinctive　characteristic　monomer　absorption　than　the　free　ZnPcC1,　which　is　a　property　beneficial　to　photodynamic　therapy.　Covalent　conjugation　results　in　the　Q-band　of　ZnPcC1　red-shifting　about　5　nm,　whereas　non-covalent　conjugation　does　not　lead　to　red-shift.