Large-scale transcriptome projects have shown that the number of RNA transcripts not coding for proteins (non-coding RNAs) is much larger than previously recognized. High-throughput technologies, coupled with bioinformatics approaches, have produced increasing amounts of data, highlighting the role of non-coding RNAs (ncRNAs) in biological processes. Data generated by these studies include diverse non-coding RNA classes from organisms of different kingdoms, which were obtained using different experimental and computational assays. This has led to a rapid increase of specialized RNA databases. The fast growth in the number of available databases makes integration of stored information a difficult task. We present here NRDR, a Non-coding RNA Databases Resource for information retrieval on ncRNA databases (www.ncrnadatabases.org). We performed a survey of 102 public databases on ncRNAs and we have introduced four categorizations to classify these databases and to help researchers quickly search and find the information they need: RNA family, information source, information content and available search mechanisms. NRDR is a useful databases searching tool that will facilitate research on ncRNAs.