Meis1 and Meis2 are highly similar homeodomain transcription factors that regulate organogenesis through cooperation with Hox proteins. Overexpression experiments have suggested an essential role for Meis factors in limb proximo-distal patterning; however, loss-of-function experiments supporting this notion have not been reported. Meis1 and Meis2 are coexpressed during limb development, first in the lateral plate mesoderm, before limb induction, and then they become restricted to a proximal domain of the growing limb bud. Here, we report that complete double conditional Meis1/2 inactivation in the lateral plate mesoderm leads to limb agenesis. Meis factors cooperate with Tbx factors in this function, extensively co-binding with Tbx to genomic sites and co-regulating enhancers of fgf10, a critical factor in limb initiation. Limbs with three deleted Meis alleles develop a complete PD set of limb skeletal elements, but show proximal-specific skeletal hypoplasia and agenesis of posterior skeletal elements. This failure in posterior skeletal element specification reveals an early role of Meis factors in establishing the limb AP prepattern required for Shh activation at later stages. Our results uncover novel roles for Meis transcription factors in early limb development and identify their involvement in new molecular interaction networks that regulate organogenesis. Overall design: Transcriptomic analysis comparing Meis1Ko;Meis2KO mutant limbs and WT limbs. RNA was isolated from the two hindlimbs E10 (30-31 somites approximately) of individual embryos. Six mutant and five WT embryos were used for analysis.