MOTIVATION: Circular dichroism (CD) spectroscopy is one of the most versatile tools to study protein folding and to validate the proper fold of purified proteins. Here, we aim to provide a readily accessible, user-friendly and platform-independent tool capable of analysing multiple CD datasets of virtually any format and returning results as high-quality graphical output to the user. RESULTS: CAPITO (CD Anaylsis and Plotting Tool) is a novel web server-based tool for analysing and plotting CD data. It allows reliable estimation of secondary structure content utilizing different approaches. CAPITO accepts multiple CD datasets and, hence, is well suited for a wide application range such as the analysis of temperature or pH-dependent (un)folding and the comparison of mutants. AVAILABILITY: http://capito.nmr.fli-leibniz.de. CONTACT: [email protected] or [email protected] SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.