Peyer's patch and nasal-associated lymphoid tissue (NALT) are mucosal lymphoid tissues that appear similar in structure and function. Surprisingly, we found that NALT, unlike Peyer's patch, was formed independently of lymphotoxin (LT)α. Furthermore, using mice deficient in the retinoic acid receptor-related orphan receptor-γ, we found that NALT was formed in the absence of CD4+CD3- cells, which are thought to be the embryonic source of LTα. However, we also found that NALT of LTα-/- animals was disorganized and lymphopenic, suggesting that the organization and recruitment of lymphocytes within NALT remained dependent on LTα. Finally, we demonstrated that both the structure and function of NALT were restored in LTα-/- animals upon reconstitution with normal bone marrow. These results demonstrate that the organogenesis of NALT occurs through unique mechanisms.