Abstract Any scholarly description of Hungarian dialects may only be possible for the time period after the settlement of the Hungarian-speaking population in the Carpathian Basin. Research in historical dialectology has primarily focused on the phonological characterization of 11th-14th century conditions, while in terms of sources, scholars have so far relied primarily on early data related to tribes’ names, historical data recorded in charters, today’s dialects, as well as evidence provided by related languages and elements borrowed from others. My paper sets out to establish the value of various sources in historical dialectology in view of our current knowledge in language history and calls attention to related methodological pitfalls. As most of these source types may also greatly contribute to the better understanding of the history of other languages, these methodological issues are relevant not only for Hungarian historical linguistics and dialectology but also more generally. The research and writing of this essay has been supported by the University of Debrecen and the MTA Premium Postdoctoral Research Program, Eötvös Loránd Research Network.