The purpose of this study was to analyze the association between the severity of inflammatory endplate changes (Modic) on MRI and the clinical response to intradiscal injection of corticosteroids (IDIC) in chronic low back pain (LBP). A total of 74 patients with LBP and inflammatory Modic changes who showed no response to 3-month conservative treatment received lumbar IDIC. Two spine specialists and a radiologist assessed independently the endplate marrow changes of the injected discs. We classified patients with a pure edema endplate changes on MRI as Modic type I (n = 37); those with a mixture of Modic type I and type II changes but predominantly edema changes as Modic I-2 (n = 25) and those with predominantly fatty changes as Modic II-1 (n = 12). The primary outcome was the change in LBP intensity between baseline and 1 month after IDIC, as measured on a visual analog scale (range 0-100 mm). At 1 month, reduction in pain score was significantly higher in the Modic I and Modic I-2 groups than in the Modic II-1 group (30.2 +/- 26.6 and 29.4 +/- 21.5 vs 5.3 +/- 25.5; P = 0.009 and P = 0.017, respectively). At 3 and 6 months, IDIC tended to be more effective in the Modic I and Modic I-2 groups but not significantly. No complications such as infection or hematoma were reported. IDIC could be a short-term efficient treatment for patients with chronic LBP and predominantly inflammatory endplate changes when conservative treatments have failed.