The objective of this study was to assess the childhood growth of twin children in terms of the effects of intrauterine growth retardation (IUGR) and discordancy at birth on the incidence and severity of stunting and discordancy in current height and weight. The study was part of a cross-sectional field project conducted at the Annual Twins Days Festival in Twinsburg. Ohio, USA, during 1990, 1991, and 1993, and including all twin children between 2 and 12 years of age. Mothers of twins were interviewed regarding their children's birthweights and gestational age; the twin children were measured for their current heights and weights. The study population included 990 twin children, including 555 boys and 435 girls, of which there were 254 boy pairs and 194 girl pairs. Birthweight for gestational age and current weight and height were each converted into Z-scores and characterized as severe (Z-score <−2,0), or moderate IUGR or stunting (Z-score > −2.0 and < −1.2). For the present study discordancy in birthweight, and current height and weight was calculated for like-gender twin pairs. Only twin children with severe IUGR at birth showed an increased risk of stunting in their current height or weight, and this risk was only for moderate, not severe, stunting. Boy twins with severe IUGR at birth were at increased risk of moderate stunting in their current weight (OR 2.67, 95% CI 1.55, 4.58, P = 0.002), while girl twins with severe IUGR at birth were at increased risk of moderate stunting in their current height (OR 4,09, 95% CI 1.49, 10.99, p = 0.003). Among like-gender twin pairs, there were no differences in mean or categories of birthweight or current weight discordancy, but boy twin pairs did show a significantly greater proportion of current weight discordancy compared to girl twin pairs (p = 0.005). Overall, there was a significant tendency for differences in height and weight between like-gender twin pairs to disappear over time, with the effect being greater for boy twin pairs. We conclude from these findings that twin children tend to overcome growth retardation and discordancy present at birth, and although children who had severe IUGR or discordancy at birth were more likely to have some residual moderate stunting or discordancy in height or weight, they still tended to be within normal values for their gender and current age.