The great tit (Parus major) has been considered to be the most typical example of an avian ring species. The terminal taxa of the ring (major and minor sectors) are supposed to be reproductively isolated in a zone of secondary contact in the middle Amur valley, Siberia. Our study combines molecular markers (cytochrome-b), bioacoustic analyses and morphological characters to judge the ring species status of the great tit complex. Despite a notable percentage of intermediately coloured birds in the mixed population of middle Amur, a lack of mitochondrial introgression between the major and minor sectors and a small number of true hybrids among voucher specimens from this area suggest at least a partial reproductive barrier between both sectors. In contrast, variation of morphological and especially acoustic characters along the ring-shaped area and the phylogenetic structure of the P. major group do not match the ring species concept. Bioacoustic and molecular data (cytochrome-b sequences) reveal two large and closely related subspecies blocks, the sectors major and bokharensis in the Western Palaearctic and central Asia, and the sectors minor and cinereus in the Eastern Palaearctic and South-east Asia, respectively. The two western sectors diverged only recently (0.5 Mya) and they were separated from the eastern group by Pleistocene events about 1.5 Mya. Songs from allopatric regions of the two subspecies blocks differ distinctly in frequency parameters and element composition. In the area of secondary contact, males of all phenotypes share the same frequency range of song, close to the range of the typical minor song. Hybrids and major males sing mixed repertoires of typical major and minor strophe types as well as mixed strophes. In contrast, phenotypic minor males display only pure minor strophes. Differences in mate choice and mating success based on repertoire size are believed to uphold the reproductive barrier between major and minor birds in the area of sympatry. Taxonomic consequences suggest three separate species in the Parus major complex: Parus major s.s. (including the very closely related bokharensis sector), Parus minor and Parus cinereus. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86, 153–174.