Extremely premature infants are at risk of developing a potentially blinding eye disease, called retinopathy of prematurity (ROP). Currently available treatment, consisting of laser surgery or injection of drugs into the eye balls, may prevent most but not all cases of permanent ROP-mediated blindness. Both types of treatment are associated with significant costs and side effects. An orally administered drug commonly used to treat hypertension, propranolol, may be effective in halting progression of ROP to severe stages, as suggested by preliminary data from small studies. As severe (threshold) ROP is an overall rare disease, the effectiveness of propranolol in combating ROP can only be assessed in a large, multicenter randomized controlled trial involving hospitals caring for extremely preterm infants of diverse origin.