UVA and UVB radiation from the sun are known to alter immune responses in both animal models and humans.  UVB can suppress both primary and secondary immune responses.  However, the role of UVA in modulating immunity is far more complex and controversial.  In this review, we discuss some recent advances we have made in the understanding of how UVA (and solar-simulated UV) affects the immune system.  The cellular responses as well the chemical and molecular mediators known to play a role in this phenomena will be discussed in the context of our and other observations.