A brief description is presented of various ways in which mixed absorption‐dispersion modes can arise. Exact closed‐form solutions are derived for the line parameters of zeroth derivatives of Lorentz shape functions containing arbitrary linear mixtures of absorption and dispersion. The parameters are obtained as functions of &egr;, where &egr; represents the fractional admixture of one signal component relative to the other, and may be determined experimentally from the signal‐amplitude asymmetry. Very simple expressions are also derived for the mixed first derivative curves if terms of the order of &egr;3and higher are neglected. In the case of the 1:1 admixture, this procedure introduces an uncertainty in the position of the line center of approximately 1% of the half‐width of the pure absorption curve. The implications of this analysis for practical spectroscopic measurements are discussed. In particular, a very simple relationship is shown to exist between the degree of admixture and the experimental variables.