State-to-state rotational energy transfer (RET) coefficients were determined for inelastic collisions of OH (A 2[Sigma]+, v'=0) with N2, CO2, and H20 at 300K. The experimental procedure described previously allows the direct evaluation of state-specific RET coefficients from timeresolved laser-induced fluorescence (LIF) measurements without any assumptions on the RET. The results show strikingly different RET behaviour for the three collision partners. The data can serve as a basis for a comparison with dynamic collision models.