Spin-orbit MRD-CI calculations have been carried out for the potential energy surfaces of the seven lowest-lying electronic states of the BiOH molecule by employing relativistic effective core potentials. The HBiO isomer is found to be 4020 cm 01 less stable because of its inability to form multiple Bi -O bands. A bent 3 A ะ BiOH ground state is predicted, which is split into all three of its components by spin-orbit coupling. The calculated X ห2 A ะ -X ห1 A splitting is computed to be 5217 cm 01 , but the corresponding X ห3 -X ห2 value is only 29 cm 01 . Fink et al. have observed spectral bands which appear with a T e value of 6200 cm 01 which are likely caused by BiOH. Since calculations at the same level for BiF underestimate the observed X ห2 -X ห1 spin -orbit splitting by 650 cm 01 , it appears that the present calculations are consistent with this experimental assignment. A vibrational progression with a 500 cm 01 frequency is also observed and this result fits in well with the computed Bi -O stretch v e value of 527 cm 01 . The calculations also find a relatively large 1 D splitting ( 600 cm 01 ) because of the bent BiOH geometry, with comparatively strong transitions to the X ห1 A ground state, and it is suggested that the experimental BiOH assignment can be confirmed on this basis. Much stronger transitions to the 1 D component should also be observed in emission in the 10 000 cm 01 range.