In the present retrospective study we determined the frequency of glucose intolerance in active untreated acromegaly, and searched for risk factors possibly supporting the emergence of the diabetic condition. Among 43 patients, 8 (19%; 95% CI: 8-33%) had diabetes mellitus and 2 (5%; 1-16%) impaired glucose tolerance. No impaired fasting glycemia was demonstrable. The frequency of diabetes was on average 4.5 times higher than in the general Slovak population. Ten factors suspected to support progression to glucose intolerance were studied by comparing the frequency of glucose intolerance between patients with present and absent risk factors. A family history of diabetes and arterial hypertension proved to have a significant promoting effect (P<0.05, chi-square test). A significant association with female gender was demonstrated only after pooling our data with literature data. Concomitant prolactin hypersecretion had a nonsignificant promoting effect. In conclusion, the association of active untreated acromegaly with each of the three categories of glucose intolerance (including impaired fasting glycemia, not yet studied in this connection) was defined as a confidence interval, thus permitting a sound comparison with the findings of future studies. Besides a family history of diabetes, female gender and arterial hypertension were defined as additional, not yet described risk factors.