miRDB is an online database for miRNA target prediction and functional annotations in animals. All the targets were predicted by a new bioinformatics tool, which was developed by analyzing thousands of genes impacted by miRNAs with an SVM learning machine. Common features associated with miRNA target binding have been identified and used to predict miRNA targets. miRDB hosts predicted miRNA targets in five species: human, mouse, rat, dog and chicken. Registration not required.