Both monomeric and:aggregated (polymeric) forms of Triton X-114 in aqueous solution are found to sensitize the fluorescence of solubilized perylene. There is evidence of strengthened monomer-acceptor association in the aqueous phase that is formed at the cloud point. In the detergent phase, no monomer excitation is observed, but sensitization by aggregates is strong. However, the emission intensity is only 67% of what is expected from probe distribution effects, indicating the thermal agitation at the cloud point is sufficient to disturb the relatively weak donor-acceptor association. In "artificially" prepared detergent phases, the sensitized emission intensity increases with detergent content and suggests an environmental change around 30% Triton X-114. Donor-acceptor distances between the detergent donor and associated perylene in aqueous solution decrease with increasing concentration, but as the micelles grow, the distance increases again. Monomer-excited sensitization shows that the micellar environment includes detergent species that are relatively loosely associated. The micellar aggregate does not act as a single polymeric donor, but appears to be excited in smaller subsegments.