Background: Light therapy is a common mode of treatment for musculoskeletal injuries but the depth of penetration of light radiation is controversial. Evidence exists for the efficacy of intense pulsed light (IPL) treatment for the rejuvenation of skin (superficial tissue) but it is not known if the IPL can penetrate deeper. If the IPL can penetrate to the depth of the Achilles tendon it may provide a potential management options in the treatment of a chronic mid-body Achilles tendinopathy. Objectives: To examine if any optical radiation produced by an IPL transmits to the depth of the Achilles tendon when applied cutaneously to excised samples of human Achilles tissue. A secondary aim was to establish the relative amount of optical radiation that was attenuated within the tendon. Materials and Methods: Three samples of human Achilles tendon and surrounding tissue were harvested following elective lower limb amputation operations. Each sample was irradiated 2-6 cm above the insertion into the calcaneus (area of an Achilles tendinopathy) with IPL (model iPulse; Cyden Ltd, Wales, UK) set at a single pulse of 25 millisecond, wavelength range 530-1,110 nm and fluence of 13 J/cm 2. The transmission of light radiation was evaluated using (a) standard SLR digital camera, (b) spectrometer, and (c) an external energy meter. Results: Light radiation was found to have transmitted through each of the three tissue samples by all three instruments. There were observable differences in the color of light detected for the control photo and the IPL irradiated tissue samples photographs. The percentage of fluence that was detected to have transmitted through the tissue samples by the energy meter was 4-8.1% and wavelengths between 645 and 843 nm were detected to have transmitted through the tissue by the spectrometer. In addition, the percentage of light radiation that attenuated with the tendon was 10.2-17.32%. Conclusion: The results of this study provides evidence that IPL penetrates to the depth of the Achilles tendon and attenuates with the tendon. IPL has potential to produce physiological effects in the treatment of patients with a chronic mid-body Achilles tendinopathy.