Dynamic palatographic techniques were used to measure the palatal boundaries of the medial groove during production of /s/ and /z/ by normal speakers. Test words were embedded in the carrier sentence “Say haCVC again,” with V = /ae/ or /i/ and presented randomly. Palatal morphology information was obtained from measurements on stone dental models of the speakers' hard palates. Results indicate that palatal morphology influences /s/ and /z/ medial groove location and accounts for some laterality effects. Medial groove parameters were essentially the same for /s/ as for /z/. [Work supported by NIH grant NS‐11852‐04.]