We present the spatial structure of binase, a small extracellular ribonuclease, derived from1H-NMR* data in aqueous solution. The total of 20 structures were obtained via torsion angle dynamics using DYANA program with experimental NOE and hydrogen bond distance constraints and φ and χ1dihedral angle constraints. The final structures were energy minimised with ECEPP/2 potential in FANTOM program. Binase consists of three α-helices in N-terminal part (residues 6- 16, 26-32 and 41-44), five-stranded antiparallel β-sheet in C-terminal part (residues 51-55, 70-75, 86-90, 94-99 and 104-108) and two-stranded parallel P-sheet (residues 22-24 and 49-51). Three loops (residues 36-39, 56-67 and 76-83), which play significant role in biological functioning of binase, are flexible in solution. The differences between binase and barnase spatial structures in solution explain the differences in thermostability of binase, barnase and their hybrids.