The present study explores the phonetic and phonological grounds on which postalveolar fricatives in Polish can be analysed as retroflex, and considers whether postalveolar fricatives in other Slavic languages are retroflex as well. Velarization and incompatibility with front vowels are introduced as articulatory criteria for retroflexion, based on cross-linguistic data. According to these criteria, Polish and Russian have retroflex fricatives (i.e., /[small s with hook]/ and /[small z with retroflex hook]/), whereas Bulgarian has a laminal palatoalveolar fricative ((/[small Esh]/). In addition, it is illustrated that palatalization of retroflex fricatives in Slavic languages (and in general) causes a phonetic and phonological change to a non-retroflex fricative.