Imposex is the development of male sexual characters onto the reproductive system of female prosobranch gastropods, phenomenon historically associated to organotin compounds. In the present study we assess the incidence of imposex in the marine snails Acanthina monodon and Nassarius coppingeri with samples collected from different localities between golfo Reloncaví and golfo Corcovado, southern Chile, which were obtained by the CIMAR 11 Fiordos Cruise. Percentage of imposex varied among localities and between the species. The imposex incidence in A. monodon ranged from 0.0 to 52.9% whereas in N. coppingeri was 11.8%. The Relative Penis Length Index (RPLI) ranged from 4.8 at Compu-Queilén to 13.3 at golfo de Ancud in A. monodon while in N. coppingeri was equal to 6.0 at Dalcahue-Quinchao. Although in this work no chemical studies were done, the development of imposex suggests the presence of organotin compounds in the studied areas.