The molecular picture of partial dynamic tube dilation (partial-DTD) was tested for monodisperse high-M star polyisoprenes (PI) with the number of entanglements per arm, N-a = 12 and 16. To achieve this test on an experimental basis, linear viscoelastic measurements were made for entangled binary blends of these high-M star PI in matrices of lower-M star PI having N-a, = 2-8. In the blends, the high-M star PI was dilute and entangled only with the lower-M matrix stars. Constraint release (CR) relaxation process was viscoelastically detected for those dilute high-M stars. The terminal CR mode was close to that expected for the Rouse relaxation of a tethered 2 chain, and the terminal CR relaxation time at 40 degrees C was described by an empirical equation, /s congruent to 4.0 x 10(-5)N(a2)(2) exp(0.71N(a1)) with N-a1 and N-a2 being the number of entanglement segments per arm of the matrix and CR) data were extrapolated to the monodisperse systems of the high-M stars (where N-al probe chains. These data to give the longest CR relaxation time tau([2m])(CR) in these systems, and the tau([2m])(CR) data were utilized to estimate the maximum possible number beta*(t) of entanglement segments at time t that were mutually equilibrated through the Rouse-CR mechanism. The corresponding normalized viscoelastic relaxation function for the partial-DTD process, mu(p-DTD)(t) = phi'(t)/beta*(t) with phi'(t) being the dielectrically evaluated survival fraction of the dilated tube, was close to the mu y(t) data, suggesting that the partial-DTD picture serves as a good starting point for describing the entanglement dynamics of monodisperse stars.