To study the prevalence of recognized and unrecognized hyperglycaemia (defined as fasting blood glucose > or = 140 mg/dL and/or random blood glucose > or = 200 mg/dL on two or more occasions), data were collected from Jordan University Hospital on all hospital deaths in those > or = 20 years of age, for the years 1995-97. The prevalence of diagnosed diabetes was 35.3% and 19.2% were missed cases of hyperglycaemia; of the missed cases, 65.7% had a blood glucose level > 250 mg/dL. Thus, the prevalence of missed hyperglycaemia among hospitalized patients is high, and greater vigilance needs to be exercised by physicians and other health professionals in reviewing laboratory results, especially those related to diabetes.