OBJECTIVE Proton pump inhibitors (PPI) and H2-receptor antagonists (H2RA) are commonly prescribed for the treatment of mild to moderate reflux esophagitis (MMRE). There remains great controversy in their usefulness as the first choice and the appropriateness. We prospectively compared the efficacy and safety of the 8-week low-dose PPI vs. standard-dose H2RA in MMRE. METHODS One hundred patients with MMRE were randomized to receive either low-dose of omeprazole (L-OMP: 10 mg, q.d.) or standard-dose of ranitidine (S-H2RA: 150 mg, b.i.d.) for 8 weeks. The H. pylori status using rapid urease test, histological examination and culture, reflux esophagitis (RE) grading, gastrointestinal symptoms using 4-point scale, adverse event and the standard laboratory examination were assessed at baseline and 8-week end point of therapy. RESULTS Improvement rate of RE [intention to treat (n=82)/per protocol (n=72)] were shown in 69.1%/63.9% for L-OMP and 65.0%/63.9% for S-H2RA group (p=0.697, p=1.000). Complete healing rates of RE were 54.7%/50.0% for L-OMP and 42.5%/41.7% for S-H2RA. No significant difference in healing rate, the rapidity of symptom resolution, adverse events, and laboratory monitoring was found between the two groups. CONCLUSIONS The low-dose omeprazole therapy produced similar healing rates and safety in the treatment of MMRE. In addition, L-OMP is advantageous in its once-a-day dosing and might be an alternative to S-H2RA, especially in Korean patients with MMRE.