The protocol for a prospective, randomized, double-blind, placebo controlled trial of iron prophylaxis in infants is described. Specific design points discussed include (i) control and "blind", (ii) dose, preparation and age of administration of iron, (iii) standardization of morbidity recording, (iv) data analysis and (v) ethics. The study cohort at birth is described and rationale for exclusions and reasons for withdrawals are discussed. An initial descriptive comparison is made of treatment and control groups entering the trial at two months of age.