UNLABELLED: The significance and function of posttranscriptional cytosine methylation in poly(A)RNA attracts great interest but is still poorly understood. High-throughput sequencing of RNA treated with bisulfite (RNA-BSseq) or subjected to enrichment techniques like Aza-IP or miCLIP enables transcriptome wide studies of this particular modification at single base pair resolution. However, to date, there are no specialized software tools available for the analysis of RNA-BSseq or Aza-IP data. Therefore, we developed meRanTK, the first publicly available tool kit which addresses the special demands of high-throughput RNA cytosine methylation data analysis. It provides fast and easy to use splice-aware bisulfite sequencing read mapping, comprehensive methylation calling and identification of differentially methylated cytosines by statistical analysis of single- and multi-replicate experiments. Application of meRanTK to RNA-BSseq or Aza-IP data produces accurate results in standard compliant formats. AVAILABILITY AND IMPLEMENTATION: meRanTK, source code and test data are released under the GNU GPLv3+ license and are available at http://icbi.at/software/meRanTK/ CONTACT: [email protected].