In this study, high-intensity, UV-A (ranging from 360 to 370 nm, peak wavelength at 365 nm) produced by a light-emitting diode was used for the inactivation of MS2 phage and Cryptosporidium parvum oocyst. In the irradiation experiment with MS2 phage, approximately 44 and 65 J/cm² of UV-A were required to obtain -2 and -3 log inactivations, respectively. The -2 and -3 log inactivations of Cryptosporidium oocysts required 338 and 508 J/cm² UV-A, respectively, which were 7.7 - 7.8 times greater than those required for MS2 phage. The possibility that high-intensity UV-A irradiation can inactivate both protozoa and viruses (phage) was demonstrated in this study.