In addition to their basic biological interest, models of reconstructed epidermis provide useful tools for in vitro assessment of the toxicology and efficacy of new chemicals and drugs. The fact that the majority of these in vitro models are composed only of keratinocytes has excluded their use in the fields of skin pigmentation and immunology. After the successful introduction of functional melanocytes into the epidermal reconstruct, the integration of Langerhans cells remains an important challenge, particularly since after isolation of Langerhans cells from human epidermis, these cells cannot be subcultured and do not integrate into the reconstructing epidermis. The authors show that cord blood derived and CD34+ progenitors isolated from the peripheral blood give rise to residential Langerhans cells when co-seeded with normal human keratinocytes.