The　issue　of　dimerization　is　vital　in　determining　the　optical　properties　of　dye-doped　sol-gel　materials　and　metallophthalocyanine　offers　an　excellent　opportunity　to　characterize　dimmers　from　monomers　because　of　their　identified　absorption　bands.　In　this　paper,　zinc　tetrasulfophthalocyanine　(ZnTSPc)　was　encapsulated　in　silica-xerogel　matrix　by　sol-gel　technique.　Dimerization　of　ZnTSPc　was　studied　using　UV-Vis　optical　absorption　spectra,　correlated　with　various　stages　of　the　sol-gel　process.　The　results　show　that　in　the　composites　ZnTSPc　concurrence　in　forms　of　monomer　and　dimmer,　and　dimerization　behaves　differently　in　the　sol,　gel　and　xerogel　stages.　Reasons　are　given　from　the　change　of　the　microenvironment　of　the　composites　in　which　ZnTSPc　existed.　(C)　2003　Published　by　Elsevier　Science　B.V.