Objective: The purpose of this study was to compare the penetration of 808 and 980 nm laser light through bovine tissue samples 18-95 mm thick. Background data: Low-level laser therapy (LLLT) is frequently used to treat musculoskeletal pathologies. Some of the therapeutic targets are several centimeters deep. Methods: Laser light at 808 and 980 nm (1 W/cm 2 ) was projected through bovine tissue samples ranging in thickness from 18 to 95 mm. Power density measurements were taken for each wavelength at the various depths. Results: For 808 nm, 1 mW/cm 2 was achieved at 3.4 cm, but for 980 nm, 1 mW/cm 2 was achieved at only 2.2 cm depth of tissue. Conclusions: It was determined that 808 nm of light penetrates as much as 54% deeper than 980 nm light in bovine tissue.