Summary.AS a result of eight years' experience of Piagetian research and subsequent work as a practising psychologist, certain aspects of Piaget's theories are criticised. In particular the existential status of operatory structures, the relation between logicality and understanding, and the representativeness of the tasks are questioned. Piagetian theory is seen as forcing the psychologist to adopt an artificially detached and one‐sidedly cognitive attitude towards children, and to focus interest entirely on very abstract aspects of performance. While accepting the historical importance of Piaget's contributions, it is argued that the limitations and constraints implicit in the theory seriously threaten its usefulness in practical situation