The efficacy of omeprazole therapy (40 mg daily) in H2-blocker refractory severe reflux oesophagitis (Grade II-IV; Savary and Miller classification) was investigated in 61 patients. Mean duration of reflux disease and preceding H2-antagonist treatment were 4.3 years and 15 months, respectively. Healing rates at 4, 8 and 12 weeks were 48%, 80% and 92%, respectively. There was a correlation between severity of oesophagitis and duration of omeprazole therapy necessary for healing. Three patients (5%) required higher dosages than 40 mg for healing. Symptomatic responses paralleled healing. It is concluded that omeprazole is a highly effective drug for severe reflux oesophagitis not responding to H2-blocker treatment and that 40 mg daily is the optimal dose.