Internal rotation in 1-(3-carboxyphenyl)-3,3-dialkyltriazenes has been investigated using PM3 and AM1 semiempirical molecular orbital techniques; methyl, ethyl, and isopropyl groups have been considered for the alkyl substituents. The purpose of this study is to establish a model for internal rotation about the N2-N3 axis in the mentioned class of compounds. Potential energy curves are analyzed with a truncated Fourier series approach, and a qualitative explanation for the shape of the curve is provided. Results obtained by vibrational and NMR spectroscopy are used to judge the reliability of the semiempirical methods used for the present problem. Agreement between experimental and calculated results is satisfactory for the PM3 parametrization. In contrast, when the AM1 method is used, an artifact in the potential energy curve of internal rotation about the N2-N3 axis is observed. The reason for this difference in performance of the two parametrizations used is discussed.