Micellar fibers and monolayers made of amphiphilic, cationic porphyrins are stabilized in bulk water by poly( allylamine) at pH values close to the pk(a) of the amines. Anionic polyelectrolytes, e.g., poly(vinyl sulfate), can also be used, but in order to prevent precipitation one must use a large polymer excess and start with small assemblies. The polyelectrolyte additions not only prevent precipitation of the large molecular assemblies with molecular weights far above 10(6) Da, but also draw back any monomers into the assemblies. Small absorption changes in 3 ns flash photolysis experiments became detectable only in the polymer-stabilized solutions.