There is known to be a high incidence of growth failure in children placed in foster care, but little is known about its etiology or the effect of foster care placement on subsequent growth. We monitored height and weight in a complete cohort (n=62) of children ages 1 to 6 y during the first year of foster care placement. 12 month data was available for 45 children. The group entered foster care with an overall height deficit (height z = -0.21), grew at an above average rate (velocity z = 0.33), and eliminated the height deficit by the end of the year (ht z = -0.02)(p<0.05). Weight increased (baseline wt z = 0.10; 12 month wt z = 0.38) and correlated with ht z change (r=0.385, p=0.009). Weight for expected weight-for-height-age was above average and did not change (baseline W/H z = 0.37; 12 month W/H z = 0.54). Baseline age correlated with 12 month vel z (r=.413, p=0.005) but not with change in ht z. Baseline height did not correlate with either 12 month vel z or change in ht z. Three patterns of growth were shown: 21 (47%) showed catch-up growth(height vel z = 1.34; increase in ht z > 0.25); 16 (36%) showed normal growth; 8 (18%) showed subnormal growth (height vel z = -1.49; decrease in ht z > 0.25 z). We conclude that: 1) almost ½ of children will show significant catch-up growth in the first year of foster care, indicating probable prior growth failure; 2) initial height is not predictive of future growth; simple screening of potential growth failure (such as height < 5th centile) will miss the majority of children who will show later catch-up growth; 3) a substantial minority will continue to decline across height centiles; 4) the etiology of the initial and subsequent growth failure, or of the catch-up growth in this population remains obscure.