Theoretical calculations are presented which estimate the possible magnitude of the O3/H2O derived OH interference signal resulting from the use of the laser-induced fluorescence technique in measuring natural levels of tropospheric OH. Critical to this new assessment has been the measurement of the nascent OH quantum state distribution resulting from the reaction O(1D)+H2O→2OH, and an assessment of the subsequent rotational relaxation of the 0H species when formed in high k levels.