We examined the positive predictive value of the International Classification of Diseases, 9th revision (ICD-9), codes used to identify cases of complicated peptic ulcer disease from the Saskatchewan Hospital automated database. Nonspecific and site- and lesion-specific codes were used in case detection to increase the sensitivity of the initial computer search. Review of the hospital records of 1,762 potential cases resulted in 1,375 confirmed cases. The positive predictive value of site and lesion-specific codes was about 90% and was about 70% for the nonspecific codes. Almost 50% of cases, however, would have been missed if the nonspecific codes had not been used.