The pulsed-jet Fourier transform rotational spectra of 4 isotopologues have been recorded for the most stable conformation of the molecular cluster pyridine-CH3F. Two weak C-HN and C-HF hydrogen bonds link the two subunits of the complex. Structural information on the hydrogen bridges has been obtained. The internal rotation of the CH3F subunit around its symmetry axis splits all rotational transitions into two (A and E) well resolved component lines, leading to a V3 barrier height of 1.55(1) kJ mol(-1).