The analysis of absorption and fluorescence spectra of poly(ether imide) solutions and related model compounds shows the existence of charge-transfer complexes in poly(ether imide) solutions and in poly(ether imide) solid state. A correlation is established between the fluorescence emission due to charge-transfer complexes and the aggregation state of poly(ether imide) solutions. The kinetics of aggregation of a solution and the aggregate dissociation phenomenon in dilute solution are observed from the study of fluorescence emission of poly(ether imide) solutions.