This paper investigates whether peer effects play an important role in retirement savings decisions. We use individual data from employees of a large university to study whether individual decisions to enrol in a Tax Deferred Account plan sponsored by the university, and the choice of the mutual fund vendor for people who choose to enrol, are affected by he decisions of other employees in the same department. To overcome the identification problems, we divide the departments into sub-groups (along gender, status, age, and tenure lines) and we instrument the average participation of each peer group by the salary or tenure structure in this group. Our results suggest that peer effects may be an important determinant of savings decisions.