Ab initio calculations on the valence electronic states of the BI molecule have been performed by using the entirely uncontracted all-electronic aug-cc-pVQZ (for the B atom) and Sadlej-pVTZ (for the I atom) basis sets and the internally contracted multireference singles and doubles configuration interaction method with Davidson size-extensively correction and Douglas-Kroll scalar relativistic correction. The potential energy curves of all valence states and the spectroscopic constants of bound states are fitted. It is the first time that the 12 Lambda-S states of BI molecule and all of the 23 Omega states generated from the former are studied in a theoretical way. Calculation results reproduce well most of the experimental data. The effects of the spin-orbit coupling and the avoided crossing rule between Omega states of the same symmetry are analyzed. The transition properties of the A (3)Pi(0)(+), B (3)Pi(1), and C (1)Pi(1) states to the ground-state transitions are predicted, including the transition dipole moments, the Franck-Condon factors, and the radiative lifetimes. The radiative lifetime of the C (1)Pi(1) state of BI molecule is less than 1 mus, while that of the A (3)Pi(0)(+) and B (3)Pi(1) states are the order of 1 ms. (C) 2004 American Institute of Physics.