Five IDD patients achieved strict preconception glycemic control and then underwent nine IVF-ET cycles. All patients had high E2 response with an adequate number of preovulatory oocytes retrieved and normal fertilization and cleavage rates; one conceived. Follicular fluid analysis revealed similar E2, P, A, hCG, PRL, and IGF-I levels to non-IDD controls. The source of the insulin detected in the FF of IDD patients was probably from the insulin doses administered intensively during the tight diabetes management; insulin was absent in non-IDD participants. It seems that patients with IDD have conventional responses to gonadotropin stimulation for IVF and their follicular milieu resembles that of non-IDD patients. Nevertheless, in view of the significant advantages of preconceptional diabetes control in regard to pregnancy outcome, they should be allowed to participate in IVF programs only after tight preconception metabolic control has been obtained.