The present study investigates the overgeneralisation of properties of transitivity altematiOnS in interlanguage grammars. Previous studies of the acquisition of argument structure have suggested that learners tend to make errors by overgeneralising passives (The window was broken where natives use The window broke, *The letter was arrived, *The child was cried) and overgeneralising causatives (*The postman arrived the letter , *The dentist cried the child) . A question is whether these errors are observed to the