Emerging evidence suggests that specific spatio-temporal microRNA(miRNA)expression is required for heartdevelopment.In recent years,hundreds of miRNAs have been discovered.In contrast,functional annotations areavailable only for a very small fraction of these regulatory molecules.In order to provide a global perspective for the biologists who study the relationship between differen tially expressed miRNAs and heart development,we employed computational analysis to uncover the specific cellular processes and biological pathways targeted by miRNAs in mouse heart development.Here,we utilized Gene Ontology(GO)categories,KEGG Pathway,and GeneGo Pathway Maps as a gene functional annotation system for miRNA target enrichment analysis.The target genes of miRNAs were found to be enriched in functional categories and pathway maps in which miRNAs couldplay important roles during heart development.Meanwhile,we developed miRHrt(http://sysbio.suda.edu.cn/mirhrt/),a database aiming to provide a comprehen sive resource of miRNA function in regulating heart development.These computational analysis results effec tively illustrated the correlation of differentially expressed miRNAs with cellular functions and heart development.We hope that the identified novel heart developmentassociated pathways and the database presented here would facilitate further understanding of the roles and mechanisms of miRNAs in heart development.