Literature data on statural growth effect of growth hormone (GH) treatment of children with GH deficiency (GHD) appears disappointing when treatment had late onset. It seems therefore that GH treatment should be started as early as possible, thus requiring early diagnosis. This study was undertaken: 1) to define the main characteristics of early onset GHD which may help the clinician for early diagnosis; 2) to evaluate the effect of a GH treatment on the statural growth of early onset GHD, when treatment is started before 1 year of age. Sixteen children with GHD diagnosed before 1 year of age were included in the study; all of them received a GH treatment before 1 year of age and for a minimal duration of 5 years; four had isolated GHD secondary to a GH gene deletion (type 1A GHD). Based on this series, the main anamnestic and clinical characteristics of early onset GHD are: frequent perinatal pathology, short birth height in more than half of the cases, relatively elevated birth weight in all cases, poor statural growth with neonatal onset, associated signs (hypoglycemia, special facies, micropenis, cryptorchidism, liver dysfunction). The effect of GH treatment (> or = 5 years) on statural growth was limited and transient in children with type 1A GHD, and resulted in an incomplete catch-up growth in children with sporadic GHD, their mean height remaining significantly below their target height.