Elongational flow was created by forcing dilute PS solutions across two jets in exact opposition. The retardation signal was mapped across the birefringence domain as a function of fluid strain rate, polymer concentration, MW, and solvent quality. The use of a fast polarization-modulation technique in conjunction with signal averaging increased the detection limit by over 1 order of magnitude in comparison to static-polarization experiments. Retardation could be determined at polymer concentrations down to the ppm level. The critical strain rate (epsilon over dot(c)) for molecular coil orientation was corrected for polymer dispersity by combining the birefringence curves with the MWD obtained by gel permeation chromatography. In contrast with previous investigations, it was found that epsilon over dot(c) depended on the solvent quality and scaled with polymer molecular weight (M) as similar to M(-1.5) in a poor solvent (decalin) and as M(-1.8) in good solvents (toluene and 1-methylnaphthalene). The possibility of using now birefringence to determine polymer molecular weight distribution has been assessed and compared to the more conventional technique of gel permeation chromatography. The large dispersion in the birefringence curves suggested a gradual increase in segmental orientation with the fluid strain rate instead of an abrupt coil-to-stretch transition.