The present article introduces SYLLABARIUM, a new Web tool addressing the needs of linguists, psycholinguists, and cognitive scientists who work with Spanish and/or Basque and are interested in retrieving information about several syllable-related parameters. This new online syllabic database allows the user to generate complete lists of Spanish and Basque syllables with information about the syllable frequency. Among other measures, for a given orthographic syllable, SYLLABARIUM provides its number of occurrences (i.e., the type frequency), the summed lexical frequency of the words that contain this syllable (i.e., the token frequency), and the positional distribution of type and token frequencies. The cross-language feature of SYLLABARIUM is of special interest to researchers aiming to explore the influence of the syllable in bilingualism. The Web tool is available at www.bcbl.eu/syllabarium.