IGF-II mRNA-binding proteins (IMPs) bind RNA and influence RNA synthesis and metabolism. IMP-1, also known as coding region determinant-binding protein/insulin-like growth factor II mRNA-binding protein (CRD-BP) and VICKZ1; IMP-2 (IMP2, VICKZ2, p62); and IMP-3 (KOC1, VICKZ3) contain a unique combination of RNA recognition motifs and four hnRNP K homology domains. IMP-1 is abundant in embryonal tissues and is expressed in 81% of colon cancers, 73% of sarcomas and 58.5% of breast cancers. It recognizes c-Myc, IGF-II and t mRNAs, and H19 RNA, and plays a major role in proliferation of K-562 cells by an IGF-II-dependent mechanism. IMP-2 binds the 5' UTR of IGF-II mRNA and influences tumor cell growth, in which IMP-2 is associated with apoptosis induced by tretinoin. IMP-3 knockdown by RNA interference decreases levels of IGF-II protein without affecting IGF-II, c-Myc, or β Actin mRNA and H19 RNA levels. IMP-3 is a marker for carcinomas and high-grade dysplastic lesions of pancreatic ductal epithelium.