The imposex promotion activities of six organotin compounds - tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenyltin (DPT) and monophenyltin (MPT) - were examined by injection experiments with T. clavigera (Prosobranchia; Muricidae). TPT and TBT had strong effects on the development of imposex in the rock shell. The other organotin compounds had no or less effects on the development of imposex in T. clavigera.