An　unexpected　dimerization　of　a　cryptand　L　with　N5O3　donors,　C33H45N5O3,　was　observed　in　aqueous　solution　when　L　was　treated　by　hydrochloric　acid　in　MeOH　and　washed　with　EtOH.　The　crystal　dimerization　product　is　a　complex　(H2L2)(2+.)2Cl(-.)5HCl(.)18H(2)O　(1)　(where　the　neutral　dimeric　cryptand　L-2　is　C66H90N10O6).　The　crystal　complex　L(2.)2HCl(.)3H(2)O　(2)　was　obtained　when　complex　1　was　neutralized　with　aqueous　solution　of　NaOH.　The　two　complexes　have　been　characterized　by　X-ray　diffraction,　NMR　and　MS.　The　conformation　of　L-2　in　1　is　endo-endo-endo-endo,　and　the　two　nitrogen　atoms　of　four　bridgehead　tertiary　nitrogen　atoms　of　L-2　are　protonated.　However,　conformation　of　L-2　in　2　is　endo-exo-endo-exo,　and　the　L-2　is　neutral.