It was the purpose of this study to evaluate dental age in boys with delayed puberty and to compare them with a group of normal, healthy boys. The study group consisted of eight boys with constitutional delay of growth and puberty (CDGP), older than 14 years, and with a testis volume smaller than 4 ml. The control group comprised 38 normal, healthy boys, aged between 12.4 and 14.3 years. Dental age was assessed using the Demirjian method and, on the basis of this evaluation, a dental delay score (i.e. dental age minus chronological age) was calculated in the CDGP and the control group. It was found that Demirjian's dental age assessment is a valid method for scoring dental age in Belgian boys between 12 and 14 years of age, and that CDGP boys showed a significant delay in dental development compared with normal boys (P = 0.0085). This study revealed a significant retardation in dental maturation of boys with CDGP.