Molecular aggregation of five types of maltohexaose-linked tetraphenylporphyrins in aqueous solution has been examined by means of a picosecond fluorescence spectroscopy. By changing the number of maltohexaosyl chains from 1 to 4 (HP1, HP2a, HP2b, HP3 and HP4), their hydrophilicity was controlled. Fluorescence spectral profile and its decay lifetime (10.5 ns) of HP4 are identical to those of monomeric H2TPP solution, while HP1 shows a multi-exponential decay even in low concentration. It was found that HP1 entirely forms more stable aggregates because of its high hydrophobicity, and that the aggregation behaviors of HP2's and HP3 are just between those of HP1 and HP4. (C) 2002 Elsevier Science B.V. All rights reserved.