Decreasing glycemic variability (GV) is become a criterion of glycemic control and important goal in the treatment of diabetes. Despite this importance there are only a few reports on GV using continuous glucose monitoring (CGM) patients with T2D on basal insulin. The aim of this exploratory study was to compare the GV after 12 weeks of treatment on Glargine-100U (Glar-100) or Glargine-300U (Glar-300) in T2D patients. Methods: This is 12-week, randomized with parallel arms. Ninety-four T2D subjects >18 y old with HbA1c between 7.5% -11% (9.2±0.9%) on NPH insulin ÷ OAD, were randomized to Glar-100 or Glar-300. A blinded CGM was inserted in a baseline (run-in) and after 12-week patient- driven titration period. The CGM parameter included TIR (70-180mg/dl), MAGE, CV, time in hypoglycemia and in hyperglycemia ranges were uploaded by carelink software and the GV parameters were analyzed by Glyculator software. Results: No differences between groups was found in any analysed GV parameter. The final HbA1c were similar to Glar-100 and Glar-300(8.0±1.12 and 8.15±1.04), however there were a significant difference regarding on total hypoglycemic events verified by self-monitoring blood glucose (SMBG) Glar-100 and Glar-300 groups (0.44±0.43 vs. 0.25± 0.42 episodes/patient/year respectively, p= 0.007). In exploratory analysis in the quartile that reached the HbA1c <7.4% TIR for Glar-300 group was 75.43% and 65.62% for Glar-100 (NS). Conclusion: In this exploratory study, even when we could not detect differences between GV parameters (probably due to not reaching target glycemic control), the lower risk of hypoglycemia with Glar-300 compared to Glar-100 can still be clearly shown. A tendency for longer TIR stay in the Glar-300 group vs. in the Glar-100 group was seen in the subgroup of those who reached close-to-target A1c values. Disclosure D.R. Franco: Advisory Panel; Self; Abbott, Medtronic, Novo Nordisk A/S, Sanofi. Research Support; Self; Sanofi. Speaker’s Bureau; Self; Abbott, AstraZeneca, Medtronic. G.D. Visconti: None. C. Feder: None. J. Baptista: None. A.G. Vianna: Board Member; Self; Abbott, Medtronic, Novo Nordisk A/S. Research Support; Self; Sanofi. Speaker’s Bureau; Self; Lilly Diabetes. M.T. Guimarães: None. F.V. Souza: None. L.A. Tagata: None. F. Eliaschewitz: Advisory Panel; Self; AstraZeneca, Novo Nordisk A/S, Sanofi-Aventis. Research Support; Self; Bayer AG, GlaxoSmithKline plc., Novo Nordisk A/S, Sanofi-Aventis. Speaker’s Bureau; Self; Eli Lilly and Company. Funding Sanofi