T1D patients (<20 years);(3.4%) had asthma. Asthma patients required higher doses of insulin.They were more often male (61% vs 52%, P < .01) and experienced more severe hypoglycemia (4.5 vs 3.2 events/100 pts. years, P < .01). No overall difference in HbA1c was found, with minor influences on metabolic control and complications. This evidence concerns the gene INS and type 1 diabetes mellitus.