In apparently healthy boys below the third percentile in height, the agreement of three radiologists' assessments of bone age from roentgenograms of the wrist and hand was poor, with only 62% concurrence of readings within six months. In 90% of the short boys, bone age was delayed more than 6 months (average delay, 29 months). In girls above the 97th percentile in height, the agreement between radiologists' readings of the same roentgenogram was closer with 75% concurrence within six months. The average difference between bone age and chronological age in the tall girls was only four months. The results suggest that certain standards, while adequate for the evaluation of tall girls, are not satisfactory for the estimation of bone age in boys below the third percentile in height.