A new inventory of 166 milestones and developmental tasks was designed and given to parents of 173 children with myelodysplasia to use over a 2½-year period to record their children's development. The inventory included items in the categories of self-help (including independent toileting), personal-social development, and gross motor development. The children were placed in one of four subgroups according to their level of paralysis. For each motor-level group, the percentage of those performing each item at various ages was calculated. The ages of routine performance of selected self-help and personal-social items are reported for 20, 50, and 80 percent achievement for the children for whom the data were known. There was a tendency for the less paralyzed children to learn skills more quickly than their more paralyzed peers. However, the wide age ranges within groups for learning individual skills indicate that factors other than the level of paralysis affect the rate of development, and these factors need to be identified. The data provided represent a reasonable estimate of when children with varying degrees of paralysis can first be expected to perform developmental tasks. The tables can be used to establish learning objectives and programs so that more children with myelodysplasia can learn independence at an earlier age.