Ab initio multi-reference configuration interaction calculations are carried out for ground and excited states of bromomethanol BrCH2OH to investigate photofragmentation processes relevant to atmospheric chemistry. Five low-lying excited states with vertical excitation energies between 5.8 and 7.4 eV (1(1)A", 1(3)A", 2(1)A', 1(3)A', 2(3)A') are found to be highly repulsive for C-Br elongation leading to CH2OH(X-2 A') and Br (X(2)p). Photodissociation along the C-O bond leading to BrCH2 ((XB2)-B-2) and OH (X-2 Pi) has to overcome a barrier of about 0.6-0.7 eV because the low-lying excited states 1(1)A", 1(3)A' and 1(3)A" become repulsive only after the C-O bond is elongated by about 0.2 Angstrom. (C) 2002 Elsevier Science B.V. All rights reserved.