Korean pear has been used as a traditional prophylactic agent for alcohol hangover. However, its mechanism was not investigated in human yet. Therefore, we performed a randomized single blind crossover trial with 14 healthy young men to examine effects of Korean pear juice on alcohol hangover. All subjects consumed 540 ml of spirits (alcohol conc. 20.1 v/v%) after 30 min from the intervention, i.e. placebo or Korean pear juice treatment. Blood and urine specimens were collected in time-courses (9 time-points for 15 h after alcohol consumption). The total and average of hangover severity were alleviated to 16% and 21% by Korean pear juice at 15 h after the alcohol consumption, respectively (ps<0.05). Particularly, 'trouble concentrating' was significantly improved by the pear juice treatment (p<0.05). Impaired memory, and sensitivity to light and sound were significantly improved by Korean pear juice among the subjects with ALDH2*1/*1 or ALDH2*1/*2 genotypes (ps<0.05) but not in the subjects with ALDH2*2/*2 genotype. In addition, the pear juice treatment lowered levels of blood alcohol (p<0.01). Therefore, Korean pear juice may alleviate alcohol-hangover and its detoxification of alcohol seems to be modified by the genetic variation of ALDH2.