Absolute rate coefficients for the title reaction, OH + HCHO → products (R1) were measured over the temperature range 202–399 K using the technique of pulsed laser photolytic generation of OH radical coupled to detection by pulsed laser induced fluorescence. The accuracy of the rate constants obtained was enhanced by on-line optical absorption measurements of the formaldehyde concentration. The temperature dependence of the rate coefficient is given by: k₁(202–399 K) = 9.52 × 10⁻¹⁸T^2.03 exp{636/T} cm³ molecule⁻¹ s⁻¹ with the rate coefficient at room temperature of 8.46 × 10⁻¹² cm³ molecule⁻¹ s⁻¹. The estimated total error (95% confidence) associated with the rate coefficient derived from this expression is estimated as 5% close to 300 K, increasing to 7% at the extremes of the temperature range covered. The present results, which extend the database on this reaction to cover temperatures relevant for the upper troposphere, are compared to previously published measurements, and values of k₁ for atmospheric modelling are recommended. In accord with most previous studies, we find no evidence for H atom formation in (R1).