Possible mass and bone density alterations were studied in second-generation OF1 mice exposed chronically since birth to a magnetic field of 50 Hz and 15 μT. For that purpose, 120 animals were sacrificed at the age of 12 weeks (males) and 14 weeks (females) and their femurs studied by bone densitometry. A total of 24 parameters in two groups (densitometric parameters such as total mass, total density, etc. and mechanical parameters like periosteal and endosteal circumferences, etc.) were analyzed. Statistical study showed no significant differences in exposed versus control animals. However, we observed slight alterations in some parameters such as total density, total and trabecular area, etc. that showed quantitative alterations making sexual dimorphism decrease or disappear. In other parameters, such as total mass or cortical and trabecular mass, the experimental magnetic field made sexual differences increase. These slight variations were possibly induced by alterations in the experimental magnetic field in the rhythm of sex and adrenal hormone secretion.