Dendritic cells (DCs) play a key role in the initiation of adaptive immune responses and the maintenance of immunological self-tolerance. Due to their therapeutic potential, understanding the mechanisms that guide DC differentiation and effector functions is important. The recent identification of posttranscriptional control of gene expression by microRNAs has added a novel layer of gene regulation that may be important in DC biology. The experimental work presented and discussed here indicates a role for microRNAs in DC regulation that is not covered by transcription factors. An essential role for microRNAs in DC lineage fate decisions, as well as in homeostasis, maturation and function of Langerhans cells (the epidermal DCs) is demonstrated. Thus, microRNAs regulate various aspects of DC biology and thereby contribute to the control of adaptive immune responses.