A central problem in medicine is the development of classification systems of disease adequate to describe the many manifestations by which a disease may present to the clinician. Such is the problem presented by retinopathy of prematurity (ROP). A group of 23 ophthalmologists, representing 11 countries, met over a period of two years to develop a new classification. This paper presents the classification (previously published) and the author's experience with its use in classifying the disease in 121 infants of birthweight less than or equal to 1300 grams over a 15-month period.