We report detailed spectroscopic measurements of the X(0)[Σ+1](v=0)→B(1)[Π3](v=5) transition in PbO. Using a Stark-modulated laser absorption technique, we have measured the hyperfine constant of Pb207O in the B(1) state, as well as the B(1)(v=5) rotational constant, X−B isotope shifts, etc. The hyperfine constant of the B(1) state is of interest as a benchmark for calculations of PbO electronic structure related to experiments to search for the electric dipole moment of the electron.