Accuracy of hospital discharge register data was studied by comparing 954 randomly selected abstracts to the respective medical records. The average percentages of agreement were: date of birth 98, date of admission 96, date of discharge 94, area of residence 93, principal diagnosis 91, disposition on discharge 89, marital status 84, third diagnosis 83, second diagnosis 76, social group 74, occupation 60, and source of admission 49. Accuracy of items was not related to alcohol etiology. An analysis of variance indicated that the number of items in agreement varied by both diagnosis and type of hospital.