The penetration rates of three different sunscreens into the human skin in vivo have been investigated using photoacoustic spectroscopy. A statistic treatment of the data obtained in a group of 15 healthy volunteers with constitutively light white skin is made using a nonparametric test. The results showed the discrimination between the times of propagation of the used products, evidencing the sensitivity of this technique to evaluate the penetration of topically applied substances through human skin in vivo.