Abstract
We report results of searches for charmless hadronic B meson decays to pseudoscalar ($\pi^{\pm}$, $K^{\pm}$ or $\pi^{0}$) -vector($\rho$, $K^{*}$ or $\omega$) final states. Using 9.7 million $B\bar{B}$ pairs collected with the CLEO detector, we report first observation of $B^{-}\to\pi^{-}\rho^{0}$, $B^{0}\to\pi^{\pm}\rho^{\mp}$ and $B^{-}\to\pi^{-}\omega$, which are expected to be dominated by hadronic b to u transitions. The measured branching fractions are (10.4 +3.3-3.4 +- 2.1) x 10$^{-6}$, (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 limits are set for all the other decay modes investigated.