Observation from an ongoing study with an oral iron supplementation programme in anaemic patients being conducted in Dinajpur (a northern district of Bangladesh) suggests that 70% of the iron supplemented group do not respond ( S. Rahman, personal communication). The prevalence of H. Pylori infection in the proposed study population is approximately 50%,35 and we expect that after oral iron supplementation the non responders will be 40% less among the H. pylori negative group, compared to the H. pylori positive group. To detect a difference of this magnitude at 5% level and at 80% power the sample size is calculated as follows: