Technical Abstract: Knowledge of penetration depth of UV in liquid egg is crucial in designing nonthermal UV pasteurizers. An experimental method was developed to determine penetration depth of 254 nm UV in liquid whole egg (LWE) and liquid egg white (LEW). An apparatus was assembled consisting of a bank of UV bulbs at the top, a container for egg in the middle, and a UV radiometer or second container for Escherichia coli at the bottom. The UV that penetrated through the egg was measured by the radiometer. In addition, inactivation of E. coli in buffered peptone water (BPW) due to transmitted UV was determined. Penetration depth, where the intensity of the UV decreases to 37% of the value at the surface, was 0.0066 and 0.0085 cm for LWE and LEW, respectively. The population of E. coli in BPW was reduced by 2.81 and 0.53 log at LWE depths of 0.018 and 0.027 cm, respectively. For LEW, the respective reductions were 4.85 and 1.05 log. This study indicates that, in order to process liquid egg products with UV, thin films of 0.01 to 0.02 cm depth may be required.