Personality disorders, the most important category of section F6, were studied in the ICD-10 field trial. The overall Kappa values for interrater reliability of section F6 is 0.64, for personality disorders 0.61 and for dyssocial personality 0.73. These results are very close to those of the DSM-III field trials. Subjective assessments of feasibility, suitability and goodness of fit demonstrate good acceptance of the diagnostic guidelines by the clinicians. A comparison of ICD-9, DSM-III and ICD-10 diagnoses yielded broad agreement for diagnoses of personality disorders with overlapping Kappa values of 0.91 and 0.94. The acceptance and reliability of the new classification could be increased by a number of improvements and the planned introduction of a multiaxial system.