Growth in height, bone age, and sexual maturation have been studied in asthmatic boys 2 to 20 yr of age. The mean pattern of growth in height has been analyzed mixed-longitudinally in 531 patients (1,754 measures) and seemed to be determined by a delay in physiologic maturation. The asthmatic boys' growth in height showed no retardation during infancy, a small but consistent retardation during childhood, a more pronounced delay at adolescence, and a catch-up growth toward adulthood. The mean adolescent growth spurt is delayed by about 1.3 yr. Bone age has been analyzed mixed-longitudinally in a subsample of 370 patients (660 observations) and showed a slight retardation at all ages between 6 and 13 yr. Development of pubic hair of 91 subjects analyzed cross-sectionally was definitely retarded when compared to adequate reference data. Evidence was given that factors secondary to the asthmatic syndrome are involved in the retardation of growth and development.