We report results of searches for charmless hadronic B meson decays to pseu
doscalar (pi*(-), K*(-), pi(0), or K-S(0))-vector(rho, K*, or omega) final
states. By using 9.7 X 10(6) B (B) over bar pairs collected with the CLEO d
etector, we report the first observation of B- --> pi(-)rho(0), (B) over ba
r(0) --> pi(-)omega, and B- --> pi(-)omega, which are expected to be domina
ted by hadronic b --> u transitions. The measured branching fractions are (
10.4+/-(3.3)(3.4)+/-2.1), (27.6+/-(8.4)(7.4) +/- 4.2) X 10(-6), and (11.3 /- (3.3)(2.9) +/-1.4) X 10(-6), respectively. Branching fraction; upper lim
its are set for all of the other decay modes investigated.