The crystal structure of the compound C₁₃H₁₆N₄OS has been determined from three dimensional intensities measured with an automatic Philips PW-1100 single crystal diffractometer.It has an orthorhombic unit cell with a=20.018±0.005Å,b=8.894±0.003Åc=7.658±0.002Åz=4.The space group is D⁴₂.The atraotnre is solved by minimum function method and direct phase determination with Multan.The positional and vibrational parameters with anisotropic temperature factors for the non-hydrogen atoms arc refined by full-matrix least square calculations to a final R=0.072 and R_W=0.051.The result of struo Wral analysis establishes beyond doubt that the diethyla.mino group is a rather strong angochrome group.