Abstract: The present study was conducted to compare the age of puberty, body weight at puberty and progesterone concentration ((P 4 conc.) during the luteal phase of the first pubertal oestrous cycle of pure Nubian doelings with those of crossbred "Nubian ? Saanen" (Experiment I). Furthermore, the influences of prepubertal GnRH injection on the age of puberty and P 4 conc. during the luteal phase of the first pubertal oestrous cycle of pure Nubian doelings were also investigated (Experiment II). In experiment I, a total of 24 doelings were employed (12 pure Nubian and 12 crossbred). The crossbred doelings attained puberty earlier (P<0.001) than the pure ones (148.08?6.69 days and 256.3?18.07 days, respectively). Moreover, their mean body weight at puberty was significantly (P<0.001) lower than that of the pure doelings (13.62?0.2 kgs and 16.92?0.65 kgs, respectively). However, there is no significant difference (P>0.05) in the mean serum P 4 conc. of pure Nubian doelings as compared with that of crossbred ones (3.44?0.67 ng, and 3.1?2.2 ng respectively). In experiment II, 12 pure Nubian doelings were used. Six doelings were intramuscularly injected with 100 g of a synthetic GnRH and the other 6 doelings were used as control. GnRH treatment significantly (P<0.001) reduced the age of puberty (157.67?3.9 days) and increased the P 4 conc. (6.07?1.78 ng ml-1). It is concluded that crossbred Nubian doelings attain puberty earlier and at a lower body weight than pure doelings. Moreover, prepubertal treatment of pure Nubian doelings with GnRH reduces the age of puberty.