In their contribution "Third-harmonic generation microscopy in highly scattering media" [Appl. Opt. 39, 5187 (2000)], C. M. Blanca and C. Saloma apply the Monte Carlo technique to the calculation of third-harmonic generation (THG) in strongly scattering samples. In that study the authors fail to appreciate the coherent nature of both the signal-generation and the image-formation process, inherent to THG microscopy. Here we wish to clarify several points.