We have fitted to within experimental accuracy a data set for acetic acid CH 3 COOH consisting of 2103vt=0, 1111vt=1 and 634vt=2 microwave lines, using the so-called “rho axis method” and a model extended to include perturbation terms through eighth order. The previously published 2109vt=0 and 409vt=1 microwave lines have been extended by new measurements from Kharkov. The final fit requires only 62 parameters to achieve a unitless weighted standard deviation for the whole fit of 0.85 for a total of 3848 lines and includes transitions with J⩽27 (15) and |K a |⩽13 (8) for the v t =2 A (E)-species, respectively. This result represents a significant improvement over our previous fit which was dominated by v t =0 transitions. A calculation of the linestrengths of torsion–rotation transitions is also provided.