Single crystals of Na 3 As have been obtained from the elements by high-pressure-high-temperature reaction in a modified Belt-type apparatus. The compound crystallizes hexagonally, space group P6 3 cm, with a=8.7838(8) , c=8.9990(12) c/a = 1.0245 and Z=6. The structure refinement (R=0.027, R=0.017 for 303 absorption-corrected unique reflections) shows unequivocally that Na 3 As is isostructural with Cu 3 P and that the structure models proposed by Brauer and Zintl (referred to as @'Na 3 As type@' in the literature, space group P6 3 /mmc) and Mansmann (anti-LaF 3 , type, space group P3cl) are wrong.