The rotational spectrum of the semistable HC_5_N molecule has been investigated in the millimeter-wave region for eight excited bending states which lie below 500cm^-1^, namely v_11_=1, 2, 3, and 4, v_10_=1, v_9_=1, (v_10_=1, v_11_=1), and (v_10_=1, v_11_=2). Transitions up to J=101-100 were measured, reaching a frequency as high as 270GHz. The set of spectroscopic constants determined in the present work makes it possible to predict much improved rest frequencies of millimeter-wave lines produced by vibrationally excited HC_5_N in hot core molecular sources and circumstellar shells. The Tables list the measured frequencies and the corresponding residuals of the least-squares analyses of J+1<--J transitions, with J in the range 8-100, which occur in the centimeter- and millimeter-wave regions.