A group of newly diagnosed patients with non-insulin-dependent (type 2) diabetes mellitus (n = 133) were divided into two groups according to the symptoms of diabetes mellitus at diagnosis; a group (26 men and 17 women) with hyperglycaemic symptoms (polydipsia, polyuria, weight loss and tiredness) and a group (44 men and 46 women) without such symptoms. At the time of diagnosis, symptomatic patients tended to be leaner (P = NS), and they were more hyperglycaemic (P less than 0.001-0.06) and had lower insulin responses to an oral glucose load (P less than 0.01-0.05) than asymptomatic patients, but after 5 years no difference in these respects was found. No significant differences in the frequency of islet-cell antibodies or cardiovascular diseases were found between the two diabetic groups. At the 5-year examination, the initially symptomatic patients were receiving pharmacological treatment for hyperglycaemia more often than asymptomatic patients. No consistent differences in clinical characteristics and 5-year outcome were observed between those diabetic patients who were diagnosed on the basis of hyperglycaemic symptoms and those who were diagnosed for other reasons. In conclusion, in middle-aged patients with newly diagnosed diabetes mellitus classified as non-insulin-dependent, diabetic symptoms at diagnosis did not predict the 5-year outcome of the patients in terms of metabolic control or cardiovascular events.