Recent observations suggest that dissipationless mergers of elliptical galaxies build up the population of massive early-type galaxies (Bell et al. 2004; Faber et al. 2006). This type of merger is observed in galaxy clusters (Tran et al. 2005) and predicted by semi-analytic models which find mass assembly times significantly later than star-formation times for the most massive elliptical galaxies (de Lucia & Blaizot 2006). Here, we use a semi-analytic model of minor mergers of dark matter halos to examine the role of dry minor mergers in elliptical galaxy formation.