We analyzed information collected during commercial hauls targeting alfonsino (Beryx splendens) on seamounts of the Juan Fernández Archipelago (Chile) from the early stages of the fishery (2001- 2003). Of the 187 hauls carried out in this period, 121 were successful; alfonsino catches reached 525.1 ton, constituting 99.2% of the total catch. Due to the irregularity of the sea bottom, short (0.26-0.50 h) fishing hauls were performed at mid-depth (469.7 m). We analyzed 14,773 specimens during the study period: 6,064 males (41%) and 8,709 females (59%), the latter being predominant. The size structure was dominated by males smaller than 24 cm fork length (LH). Average sizes fluctuated between 34.6 and 36.8 cm LH for males and between 36.2 and 38.4 cm LH for females. To determine gonad maturity, we used the macroscopic scale proposed by Lehodey et al. (1997); the males reached first maturity (TMS50%) at 34.3 cm LH and the females at 33.3 cm LH. The average yields for the study period ranged from 0.2 to 6.6 ton haul-1 and between 1.8 and 19.0 ton h.a.-1, with averages of 4.3 ton haul-1 and 9.2 ton h.a.-1.