Complex dielectric spectra of acetic acid solutions were measured at frequencies in the range of 120 GHz using an automatic network analyser at room temperature. The spectra of different commercial vinegars were also measured. All spectra follow a Debye relation for both the real and imaginary parts of permittivity. The Debye relation, with an additional term for ionic conduction losses, was fitted to the data, and six parameters were extracted. Quantitative relations between the parameters that define Debye relations and the acid contents in solution were obtained. (C) 2009 Elsevier Ltd. All rights reserved.