Second and third virial coefficients (A(2) and A(3), respectively) for cyclohexane solutions of linear polystyrene (benzyl-PS) samples, synthesized with benzyllithium (n-butyllithium/tetramethylethylenediamine/toluene ligand complex) as an initiator, were determined as functions of temperature and weight-average molecular weight M-w ranging from 710 to 7650. At the &UTheta; temperature (34.5 ° C), where A(2) = 0 for sufficiently high M-w A(2) decreased with lowering M-w in contrast to the sharp increase reported for low molecular weight polystyrene with a butyl group (butyl-PS) at one of the chain ends. This molecular weight dependence of negative A(2) for benzyl-PS was explained, without consideration of end effects, by the recent theory of Yamakawa and Yoshizaki for the helical wormlike chain with three-segment interactions, while the upswing of positive A(2) for butyl-PS was ascribed primarily to the butyl end effect that surpasses the ternary cluster effect. The A(3) values for both benzyl- and butyl-PS were positive and increased with decreasing M-w, showing significant end effects. The end effect in the former was larger than that in the latter, indicating that the three-segment interaction among a chain-end unit and two middle units for benzyl-PS is larger than that for butyl-PS.