This article investigates the development of the palatalization contrast in Slavic from diachronic, synchronic, and phonetic perspectives. The diachrony of this contrast is an important test case for theories of the actuation of sound change, since the Slavic language family shows an impressive diversity in the realization of the original contrast, with Russian, for instance, preserving the contrast, Slovak maintaining it only for some consonants, and Slovenian showing complete merger. A diachronic study of the contrast reveals a generalization about which consonant pairs are more or less likely to undergo merger, and an acoustic-phonetic study of Russian points to the aspects of synchronic phonetic variability that correlate with merger. We then use the methods of the acoustic theory of speech production and synchronic phonology to further understand the development of the sound change. The results and interpretation point to a tight interplay between phonetics and phonology in the realization of the change.