The quantum chemical calculations and IR & Raman spectra have been used to characterize the structural, energetics and vibrational properties of 2-deoxy-2-(3- methyl-3-nitrosourea)-1-D-glucopyranose (streptozotocin, STZ), which is widely used in diabetes research. The two conformers (E and Z) of the both chair and boat forms were obtained as a result of conformational analyses made for STZ. The three dimeric structures were formed by the interactions of the two most stable STZ monomers from different sites. The hydrogen bonding, HOMO-LUMO, molecular electrostatic potential (MEP) and vibrational analyses were made for monomeric and dimeric structures of STZ using HF and DFT/B3LYP methods with 6-31G(d,p) and 6-311G(d,p) basis sets. The optimized geometrical parameters of monomeric and dimeric structures were compared with the experimental structural data in the solid state. The optimized geometry and the calculated IR & Raman spectra for dimeric structure of STZ show very good agreement with the experimental ones. (C) 2020 Elsevier B.V. All rights reserved.