Objective To determine the frequency of medical encounters before diagnosis of diabetes in children in Ontario, Canada; to determine risk factors for diabetic ketoacidosis (DKA). Research design All medical encounters within 4 weeks before date of diagnosis for all new cases of diabetes in children <18 years were identified from April 1994 to March 2000 by use of administrative databases. The main outcome measure was the frequency of medical encounters before diagnosis in children presenting with and without DKA. Results A total of 3947 new cases of diabetes were identified, 735 (18.6%) with DKA. DKA rates were 39.7% for children ≤3 years and 16.3% for children >3 years ( P < .001). During the week before diagnosis, 285 children with DKA (38.8%) and 1104 children with diabetes without DKA (34.4%; P = .026) had at least 1 medical visit. Children with diabetes overall had more medical encounters before diagnosis than control subjects. Children with DKA were less likely to have had relevant laboratory testing before diagnosis than children with diabetes without DKA. Conclusions Children with diabetes presenting with DKA more frequently had a medical encounter before diagnosis compared with children with diabetes without DKA. These data have important implications for enhancing public and physician awareness of diabetes in children.