Dendritic-like polyelectrolytes (highly branched polymer cluster, HBNP) made from a phthalic anhydride/pentaerythritol polycondensation were investigated by laser light scattering (LLS) respectively in N,N-dimethylformamide (DMF) and buffer solutions. In DMF, individual HBNP dusters were studied and we found that they have a weight-average molar mass of 1.1 x 10(4) g/mol and an average hydrodynamic radius of 4.16 nm. In the buffer, the complex formation between HBNP and surfactant (cetyltrimethylammonium bromide, CTAB) was monitored by dynamic light scattering. The influence on the HBNP/CTAB complexes apparent hydrodynamic radius distribution of the HBNP:CTAB ratio, of both HBNP and CTAB concentrations, of formation time, and of pH has been examined. Our results suggested that the complex formation between HBNP and CTAB in the buffer can be modeled as the adsorption of negatively charged HBNP clusters on the cationic surface of the CTAB micelle. Further, we observed a slow aggregation of the HBNP/CTAB complexes. The stabilities of the HBNP/CTAB complex and the complex aggregates in the buffer were examined. It is found that pH can greatly influence the stabilities, which might be used in a controlled-releasing application.