Deflazacort, a new glucocorticoid (DFZ) which has recently become available, is known to have lower adverse effects on the skeletal metabolism and is expected to inhibit growth to a lesser extent in long-term treated children than earlier cortisone analogues. With the aim of verifying this hypothesis a multicenter study was planned to compare the effects of deflazacort and prednisone on linear growth and skeletal maturation in a group of prepubertal children requiring chronic steroid therapy. The data presented in this interim analysis refer to 24 children (11 females and 13 males ranging in age from 2.4 to 11.8 yrs) with rheumatoid arthritis (18), systemic lupus erythematosus (4) or dermatomyositis, selected from the total sample of 65 subjects included in the trial. They were randomly allocated to DFZ or PDN treatment and received the minimum effective dose of either steroid for at least 6 months per year. Longitudinal height measurements were obtained with standard instruments and techniques, and the bone age was assessed according to Greulich and Pyle. The following indicators of growth retardation were considered: bone age delay (difference between bone age and chronological age), statural age delay (statural age, with respect to the 50th percentile minus the chronological age) and statural age loss (statural age with respect to the individual height percentile at the first observation minus the chronological age).(ABSTRACT TRUNCATED AT 250 WORDS)