Analogues of the eukaryotic messenger RNA 5' end (m(7)G cap) are useful tools for studying mRNA fate and serve as reagents for in vitro preparation of 5' capped mRNAs. We designed a biotin-labeled dinucleotide cap analogue that can be incorporated into transcripts to produce 5'-capped and biotinylated mRNAs which retain their biological functionality and may be employed for biotin-(strept)avidin technologies.