Hydrogen breath tests were performed in eight children with sickle cell disease (Hgb S-S), four of whom were growth retarded. Average base-line breath H2 values after an overnight fast were elevated (22.4 +/- 10.8 ppm; normal = 7.1 +/- 5.0). Breath H2 concentrations increased significantly above base line within 30-40 min after lactulose ingestion in the four growth-retarded children whereas a negligible rise was observed in the four with normal growth indices. Breath H2 production for each time interval in the first 120 min was greater in all Hgb S-S then in normal children (p less than 0.01 for each time interval measured before 60 min). The results indicate that children with sickle cell disease have intestinal abnormalities favoring excess production of H2 in the fasted state combined with early elevations in postlactulose breath H2 in those with growth retardation. The possible role of disordered gastrointestinal motility and/or anomalously distributed intestinal flora in growth retardation of children with Hgb S-S requires further investigation.