background In the last edition of the dsm the externalising disorders have been fundamentally changed and have been separated from the neurodevelopmental disorders. aim To make a detailed study of the principal changes. method The old and new criteria for the behavioral disorders are compared and tested on the basis of their clinical utility, which is the underlying principle of the new dsm-5. results More justice had been done to the gradual transition from symptoms of personality disorders to the illness itself. This has been done by placing the transition under the heading ‘boundary-crossing behaviour’ and by removing the rule that no-one under the age of 18 can be diagnosed as having a personality disorder. For personality disorders, the old category has been retained but a new one is proposed. conclusion In the 5th edition of the dsm the classification of behavioral disorders is much better and clearer than in the 4th edition. Careful attention has been given to the need to ensure that the severity of a patient’s illness play a major role in the diagnosis. The classification of the personality disorders still needs further discussion.