In human cells, Staufen1 is double-stranded RNA-binding protein involved in several cellular functions including mRNA localization, translation and decay. We used a genome wide approach to identify and compare the mRNA targets of mammalian Staufen1. The mRNA content of Staufen1 mRNPs was identified by probing DNA microarrays with probes derived from mRNAs isolated from immunopurified Staufen-containing complexes following transfection of HEK293T cells with a Stau1-HA expressor. Our results indicate that 7% of the cellular RNAs expressed in HEK293T cells are found in Stau1-containing mRNPs. There is a predominance of mRNAs involved in cell metabolism, transport, transcription, regulation of cell processes and catalytic activity.