[en] Energy level of Yb-172 have been studied using the (n,n'γ) reaction with fast reactor-neutrons. The dexcitation gamma-rays from a target (5.68g of Yb₂O₃ enriched the 95.0% in Yb-172). Gamma-ray spectra, recorded at five angles (theta=90⁰, 114⁰, 125⁰, 135⁰, 145⁰) relative to the incident beam direction, were analyzed by using the peak-finding, peak-fitting computer BABIL. Spin assignments to levels in Yb-172 were carried out by comparing the experimentally determined a₂ and a₄ coefficients for each gamma-transition with those computed for range of spin sequences as a function of multipole mixing ratio delta, using the computer code CINDY. The a₂ coefficient was to deduce the allowed values of delta. 16 tabs.; 51 figs. 69 refs