Mudwhelks dominate the sessile invertebrate epifauna of many Indo-West Pacific mangroves. They can be useful in monitoring the health of mangrove communities as they have a shorter lifespan than the trees, but there are few data on the lifespan of these snails. To eliminate this gap, growth rates were obtained using data from tagging experiments fitted to the von Bertalanffy growth equation. Terebralia palustris and T. semistriata were tagged at Mandorah, Northern Territory in May 1999 and remeasured approximately every six months for two years; Telescopium telescopium was added in December 1999. Terebralia palustris and T. semistriata were tagged near Dampier, Western Australia in April 1999 and remeasured quarterly until July 2000. Both species of Terebralia grew faster and larger at Mandorah, near the centre of their ranges; growth and adult sizes were less in Dampier, near their southern range limit. The small (up to 6 cm) Terebralia semistriata matures in about four to six years, T. palustris (up to 19 cm) in 10-12 years and T. telescopium (up to 13 cm) in about 10-12 years. However, the high proportion of adults in some populations of all three species suggest the lifespans may be much longer.