We used housing assignment data from a college in China to investigate peer effects on college grades. Study results provided some evidence for peer effects in college housing units. First, peer effects through means occurred during both fall and spring semester of the first year in college, with estimated effect much larger than that in previous studies. Second, students are also influenced by the mix of roommates. Finally, having more than one roommate in the top quartile has large and significant effects for female students; however, this positive effect is not statistically significant for male students.