The diagnoses given to samples of 1,000 first admissions to English mental hospitals in 1977 and 1980 were compared in order to find out how much influence the 9th revision of the International Classification and its glossary had had on the diagnostic habits of English psychiatrists since its introduction in January 1979. Although the differences between 1977 and 1980 diagnoses were modest they were greater than those found in an earlier comparison of 1968 and 1971 diagnoses, before and after the introduction of the 8th revision. Comparison of all four sets of diagnoses, from 1968 to 1980, revealed some serial changes in the categorization of depressive illnesses and a slowly increasing familiarity with the ICD. Although a higher proportion of diagnoses used the nomenclature of the ICD in 1980 than in previous years, this was mainly because the ICD had adapted itself to the habits of English psychiatrists rather than the other way about.