BACKGROUND Diagnosis of subarachnoid haemorrhage (SAH) is firstly based on imaging and secondly on spectrophotometry. Bilirubin may be detected in the cerebrospinal fluid (CSF) for up to two weeks after SAH. CSF pigment analysis is commonly performed according to the Chalmers manual technique but may be prone to operator error. We propose an online software solution, based on the United Kingdom National External Quality Assessment Service (UKNEQAS) recommendations, to support the interpretation of CSF pigment analysis. METHODS Based on the manual Chalmers technique, we have developed a web application (in Personal Home Page language including JpGraph module and an Oracle database(®)) that enables the calculation of net oxyhaemoglobin absorbance and net bilirubin absorbance. It uses data from the CSF spectrophotometry, CSF and serum protein concentrations, and serum bilirubin concentration to provide an interpretation based on the NEQAS decision tree. The application was retrospectively validated using the spectra from 350 patients, previously analysed by the manual method. RESULTS In total, 91.1% interpretations from spectra analysed with the web application were in accordance with the results obtained manually. The 8.9% discordant results were mostly related to an incorrect interpretation using the manual technique. CONCLUSIONS The software developed in our laboratory to interpret CSF pigment analysis results is a precise, robust and useful tool that allows reproducible conclusions to be drawn. This software is available through a web interface.